Earnings Per Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Compensation and Retirement Disclosure [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plans United States Pension Plan of US Entity, Defined Benefit [Member] Postretirement Benefit Plan United States Postretirement Benefit Plan of US Entity, Defined Benefit [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Benefit Plans and Other Postretirement Benefits [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] Target Asset Allocations and Plan Assets Measured at Fair Value Schedule of Allocation of Plan Assets [Table Text Block] Changes in Level 3 Plan Assets Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block] Change in Projected Benefit Obligation Schedule of Changes in Projected Benefit Obligations [Table Text Block] Change in Fair Value of Plan Assets Schedule of Changes in Fair Value of Plan Assets [Table Text Block] Funded Status of Plans Schedule of Net Funded Status [Table Text Block] Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block] Amounts Not Yet Recognized as Components of Net Periodic Benefit Costs Recorded on the Balance Sheet Based Upon Expected Recovery in Rates Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Schedule of Assumptions Used Schedule of Assumptions Used [Table Text Block] Components of Net Periodic Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Effects of One-Percent Change in Assumed Health Care Cost Trend Rate Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block] Projected Benefit Payments for the Pension and Postretirement Benefit Plans Schedule of Expected Benefit Payments [Table Text Block] Contributions to Multiemployer Plans Schedule of Multiemployer Plans [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Environmental Contingencies [Abstract] Environmental Contingencies [Abstract] -- None. No documentation exists for this element. -- Unrecorded Unconditional Purchase Obligation [Table] Unrecorded Unconditional Purchase Obligation [Table] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Capital Commitments Capital Addition Purchase Commitments [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] NSP-Minnesota NSP Minnesota [Member] NSP-Minnesota is an operating utility engaged in the generation, purchase, transmission, distribution and sale of electricity in Minnesota, North Dakota and South Dakota. NSP-Minnesota also purchases, transports, distributes and sells natural gas to retail customers and transports customer-owned natural gas in Minnesota and North Dakota. NSP-Wisconsin NSP-Wisconsin [Member] NSP-Wisconsin is an operating utility engaged in the generation, transmission, distribution and sale of electricity in portions of northwestern Wisconsin and in the western portion of the Upper Peninsula of Michigan. NSP-Wisconsin also purchases, transports, distributes and sells natural gas to retail customers and transports customer-owned natural gas in the same service territory. PSCo PSCo [Member] PSCo is an operating utility engaged primarily in the generation, purchase, transmission, distribution and sale of electricity in Colorado. PSCo also purchases, transports, distributes and sells natural gas to retail customers and transports customer-owned natural gas in Colorado. Environmental Regulation [Axis] Environmental Regulation [Axis] Information by type of environmental regulation. Environmental Regulation [Domain] Environmental Regulation [Domain] Identifies by name or nature the environmental regulation. Federal Clean Water Act Federal Clean Water Act [Member] Regulations adopted by the Environmental Protection Agency for the Federal Clean Water Act. EPA GHG Regulation EPA GHG Regulation [Member] Regulations adopted by the Environmental Protection Agency (EPA) for Greenhouse Gas (GHG) Regulation. Electric Generating Unit Mercury And Air Toxics Standards Rule Electric Generating Unit Mercury And Air Toxics Standards Rule [Member] Regulations adopted by the Environmental Protection Agency for electric generating units (EGU) Mercury and Air Toxics Standards (MATS). Minnesota Mercury Legislation Minnesota Mercury Legislation [Member] Regulations adopted by the Minnesota Public Utilities Commission and the Minnesota Pollution Control Agency for mercury emission controls. Industrial Boiler Maximum Achievable Control Technology Rules Industrial Boiler Maximum Achievable Control Technology Rules [Member] Regulations adopted by the Environmental Protection Agency for Industrial Boiler (IB) Maximum Achievable Control Technology (MACT) to regulate boilers and process heaters fueled with coal, biomass and liquid fuels. Regional Haze Rules Regional Haze Rules [Member] Regulations adopted by the Environmental Protection Agency for Regional Haze Rules. Unrecorded Unconditional Purchase Obligation [Line Items] Unrecorded Unconditional Purchase Obligation [Line Items] Environmental Requirements [Abstract] Environmental Requirements [Abstract] -- None. No documentation exists for this element. -- Number of potential regulatory options under the proposed Effluent Limitations Guidelines rule Number of potential regulatory options under the proposed Effluent Limitations Guidelines rule The number of potential regulatory options under the proposed Effluent Limitations Guidelines rule within the Federal Clean Water Act. Number of issues granted review by the U.S. Supreme Court Number of issues granted review by the U.S. Supreme Court The number of issues granted review by the U.S. Supreme Court relating to environmental rules. Generating capacity (in MW) Minimum Generating capacity Minimum generating capacity of the facility for which the regulation affects. Number of years before affected facilities must demonstrate compliance, low end of range Number of years before affected facilities must demonstrate compliance, low end of range The low end of the range of number of years before the United States Environmental Protection Agency will require affected facilities to demonstrate compliance. Number of years before affected facilities must demonstrate compliance, high end of range Number of years before affected facilities must demonstrate compliance, high end of range The high end of the range of number of years before the United States Environmental Protection Agency will require affected facilities to demonstrate compliance. Liability for estimated cost to comply with regulation Liability for estimated cost to comply with regulation Estimated undiscounted amount of the accrual required to comply with required regulation. Number of environmental groups who petitioned the U.S. Department of the Interior Number Of Environmental Groups Who Petitioned The U.S. Department Of The Interior The number of environmental groups petitioning the U.S. Department of the Interior to certify that the coal-fired boilers and the coal-fired cement kiln in Colorado are contributing to visibility problems in Rocky Mountain National Park. Number of coal-fired boilers in Colorado Number Of Coal Fired Boilers In Colorado The number of coal-fired boilers in Colorado that are requested to be certified they are contributing to visibility problems in Rocky Mountain National Park. Number of coal-fired cement kilns in Colorado Number Of Coal Fired Cement Kilns In Colorado The number of coal-fired cement kilns in Colorado that are requested to be certified they are contributing to visibility problems in Rocky Mountain National Park. Estimated amount spent on projects to reduce NOx emissions on Sherco Units 1 and 2 Estimated amount spent on projects to reduce NOx emissions The estimated amount spent on capital projects to comply with required regulation. Valuation and Qualifying Accounts [Abstract] Schedule II, Valuation and Qualifying Accounts Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Income Statement [Abstract] Operating revenues Revenues [Abstract] Electric Electric Domestic Regulated Revenue Natural gas Gas Domestic Regulated Revenue Other Other Revenue, Net Total operating revenues Revenues Operating expenses Costs and Expenses [Abstract] Electric fuel and purchased power Cost of Domestic Regulated Electric Cost of natural gas sold and transported Cost of Domestic Regulated Gas Revenue Cost of sales — other Other Cost of Operating Revenue Operating and maintenance expenses Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses Conservation and demand side management program expenses Conservation And Demand Side Management Program Expenses Costs incurred for energy conservation, weatherization and other programs to conserve or manage energy use by customers. Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Taxes (other than income taxes) Taxes, Miscellaneous Total operating expenses Costs and Expenses Operating income Operating Income (Loss) Other income, net Other Nonoperating Income (Expense) Equity earnings of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Allowance for funds used during construction — equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Interest charges and financing costs Interest and Debt Expense [Abstract] Interest charges — includes other financing costs of $30,135, $24,087 and $24,019, respectively Interest Expense Allowance for funds used during construction — debt Allowance for Funds Used During Construction, Capitalized Interest Total interest charges and financing costs Interest and Debt Expense Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income taxes Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Dividend requirements on preferred stock Preferred Stock Dividends, Income Statement Impact Premium on redemption of preferred stock Preferred Stock Redemption Premium Earnings available to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Earnings per average common share: Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Cash dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Stock Equivalent Units [Member] Stock Equivalent Units [Member] Share-based compensation awarded to non-employee members of the Board of Directors, payable upon termination of service in either the form of stock or the cash equivalent. Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Equity Instruments Other than Options Activity [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Balance at January 1 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Units distributed (in shares) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Distributed In Period The number of units under a share-based award plan other than a stock option plan that do not need to vest and are readily available, regardless of in stock equivalents or in cash, during the period in accordance with the terms of the arrangement. Dividend equivalents (in shares) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Dividend Equivalents In Period The number of shares issuable under a share-based award plan pertaining to dividend equivalents on shares outstanding during the period on other than stock option plans. Balance at December 31 (in shares) Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Balance at January 1, weighted average grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted, weighted average grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Units distributed, weighted average grant date fair value (in dollars per share) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Distributed In Period Weighted Average Grant Date Fair Value The weighted average fair value as of grant dates pertaining to a share-based award plan other than a stock option plan for units that do not need to vest and are readily available, regardless of in stock equivalents or in cash, during the period in accordance with the terms of the arrangement. Dividend equivalents, weighted average grant date fair value (in dollars per share) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Dividend Equivalent In Period Weighted Average Grant Date Fair Value The weighted average fair value as of grant dates pertaining to a share-based award plan other than a stock option plan for dividend equivalents on shares outstanding during the period in accordance with the terms of the arrangement. Balance at December 31, weighted average grant date fair value (in dollars per share) Equity Instruments Other than Options, Additional Disclosures [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract] Number of shares of common stock into which the share-based compensation can be converted (in shares) Number of shares of common stock into which the share-based compensation can be converted (in shares) Number of shares of common stock into which the share-based compensation can be converted (in shares) Document and Entity Information [Abstract] -- None. No documentation exists for this element. -- Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Common Stock, Shares Outstanding (in shares) Common Stock, Shares, Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Fair Value Disclosures [Abstract] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Government securities US Treasury and Government [Member] U.S. Corporate Bonds Domestic Corporate Debt Securities [Member] International Corporate Bonds Foreign Corporate Debt Securities [Member] Municipal Bonds Municipal Bonds [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Final Contractual Maturity [Abstract] Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract] Due in 1 Year or Less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Due in 1 to 5 Years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Due in 5 to 10 Years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Due after 10 Years Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Total Available-for-sale Securities, Debt Maturities, Single Maturity Date Long-term Contracts for Purchase of Electric Power [Table] Long-term Contracts for Purchase of Electric Power [Table] Long-term Contract for Purchase of Electric Power [Axis] Long-term Contract for Purchase of Electric Power [Axis] Long-term Contract for Purchase of Electric Power [Domain] Long-term Contract for Purchase of Electric Power [Domain] Capacity Capacity Payments [Member] Payments for dispatch control of the energy generating facilities under purchase power agreements (PPAs) with other utilities and energy suppliers to meet system load and energy requirements, replace generation from company-owned units under maintenance or during outages, and meet operating reserve obligations. Energy Energy Payments [Member] Payments for the actual production of energy under purchase power agreements (PPAs) with other utilities and energy suppliers to meet system load and energy requirements, replace generation from company-owned units under maintenance or during outages, and meet operating reserve obligations. Long-term Contract for Purchase of Electric Power [Line Items] Long-term Contract for Purchase of Electric Power [Line Items] Purchased Power Agreements (PPAs) [Abstract] Purchased Power Contracts [Abstract] -- None. No documentation exists for this element. -- Payments for capacity Utilities Operating Expense, Purchased Power under Long-term Contracts Estimated Future Payments Under PPAs [Abstract] Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract] 2014 Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months 2015 Unrecorded Unconditional Purchase Obligation, Due within Two Years 2016 Unrecorded Unconditional Purchase Obligation, Due within Three Years 2017 Unrecorded Unconditional Purchase Obligation, Due within Four Years 2018 Unrecorded Unconditional Purchase Obligation, Due within Five Years Thereafter Unrecorded Unconditional Purchase Obligation, Due after Five Years Total Unrecorded Unconditional Purchase Obligation Activity in Stock Options Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Total Market Value and Total Intrinsic Value of Stock Options Exercised Disclosure Of Share Based Compensation Arrangements By Share Based Payment Award Options Exercised [Table Text Block] Tabular disclosure of the market value and intrinsic value of exercised stock options that have been awarded as share-based compensation to employees. Cash Received and Actual Tax Benefit from Stock Options Exercised Schedule of Cash Proceeds Received from Share-based Payment Awards [Table Text Block] Restricted Stock Schedule of Share-based Compensation, Restricted Stock Shares Award Activity [Table Text Block] Tabular disclosure of the number and weighted-average grant date fair value for restricted stock shares that were outstanding at the beginning and end of the year, and the number of restricted stock shares that were granted, vested, or forfeited during the year. Restricted Stock Units Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Stock Equivalent Unit Plan Schedule of Share-based Compensation, Nonemployee Director Stock Award Plan, Activity [Table Text Block] PSP Awards Psp Awards [Table Text Block] Tabular disclosure of Performance Share Plan (PSP) awards granted and the total amounts of performance awards settled during the period. Compensation costs related to share-based awards Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common stock Common Stock [Member] Additional Paid In Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss) [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Balance (in shares) Net income Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Dividends declared: Dividends [Abstract] Dividends, Preferred Stock, Cash Dividends, Preferred Stock, Cash Common stock Dividends, Common Stock Preferred Stock Redemption Premium Issuances of common stock Stock Issued During Period, Value, New Issues Issuances of common stock (in shares) Stock Issued During Period, Shares, New Issues Repurchase of common stock Stock Repurchased During Period, Value Repurchase of common stock (in shares) Stock Repurchased During Period, Shares Purchase of common stock for settlement of equity awards Adjustments To Additional Paid In Capital Purchase Of Common Stock For Settlement Of Equity Awards Decrease in additional paid in capital due to the purchase of shares of common stock to fulfill requirements for the employer match pursuant to various benefit plans. Share-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Balance Balance (in shares) Stockholders' Equity Note [Abstract] Other Comprehensive Income Comprehensive Income (Loss) Note [Text Block] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Commingled and international equity funds Commingled Funds and International Equity Funds [Member] An investment that pools funds from many investors to invest in a combination of underlying investments, primarily commingled and international equity investments. Real estate funds Real Estate Funds [Member] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Notice period for investment redemption (in days) Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period Quarterly Financial Information Disclosure [Abstract] Summarized Quarterly Financial Data (Unaudited) Schedule of Quarterly Financial Information [Table Text Block] Capitalization, Long-term Debt and Equity [Abstract] Schedule of Capitalization, Long-term Debt [Table] Schedule of Capitalization, Long-term Debt [Table] SPS SPS [Member] SPS is an operating utility engaged primarily in the generation, purchase, transmission, distribution and sale of electricity in portions of Texas and New Mexico. Other Subsidiaries Subsidiaries [Member] Xcel Energy Inc. Parent Company [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] First Mortgage Bonds Bonds [Member] Senior Unsecured Notes Unsecured Debt [Member] City of La Crosse Resource Recovery Bond [Member] City of La Crosse Resource Recovery Bond [Member] Recovery bonds issued by the City of La Crosse, Wisconsin. The bonds were issued for the purpose of refunding a 1986 series. Fort McCoy System Acquisition [Member] Fort McCoy System Acquisition [Member] Debt issued in connection with the Fort McCoy System Acquisition. Capital Lease Obligations [Member] Capital Lease Obligations [Member] Various Eloigne Co. Affordable Housing Project Notes [Member] Various Eloigne Co. Affordable Housing Project Notes [Member] Notes issued in connection with investments in various affordable housing projects by the Company's non-regulated wholly-owned subsidiary, Eloigne Company. Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Series Due Aug. 15, 2015 [Member] Series Due Aug. 15, 2015 [Member] Series of First Mortgage Bonds due August 15, 2015. Series Due March 1, 2018 [Member] Series Due March 1, 2018 [Member] Series of First Mortgage Bonds due March 1, 2018. Series Due Aug. 15, 2022 [Member] Series Due Aug. 15, 2022 [Member] Series of First Mortgage Bonds due Aug. 15, 2022. Series Due May 15, 2023 Series Due May 15, 2023 [Member] Series of First Mortgage Bonds Due May 15, 2023 Series Due July 1, 2025 [Member] Series Due July 1, 2025 [Member] Series of First Mortgage Bonds due July 1, 2025. Series Due March 1, 2028 [Member] Series Due March 1, 2028 [Member] Series of First Mortgage Bonds due March 1, 2028. Series Due July 15, 2035 [Member] Series Due July 15, 2035 [Member] Series of First Mortgage Bonds due July 15, 2035. Series Due June 1, 2036 [Member] Series Due June 1, 2036 [Member] Series of First Mortgage Bonds due June 1, 2036. Series Due July 1, 2037 [Member] Series Due July 1, 2037 [Member] Series of First Mortgage Bonds due July 1, 2037. Series Due Nov. 1, 2039 [Member] Series Due Nov. 1, 2039 [Member] Series of First Mortgage Bonds due November 1, 2039. Series Due Aug. 15, 2040 [Member] Series Due Aug. 15, 2040 [Member] Series of First Mortgage Bonds due August 15, 2040. Series Due Aug. 15, 2042 Series Due Aug. 15, 2042 [Member] Series of First Mortgage Bonds due Aug. 15, 2042. Series Due March 1, 2013 [Member] Series Due March 1, 2013 [Member] Series of First Mortgage Bonds due March 1, 2013. Series Due April 1, 2014 [Member] Series Due April 1, 2014 [Member] Series of First Mortgage Bonds due April 1, 2014. Series Due Sept. 1, 2017 [Member] Series Due Sept. 1, 2017 [Member] Series of First Mortgage Bonds due September 1, 2017. Series Due Aug. 1, 2018 [Member] Series Due Aug. 1, 2018 [Member] Series of First Mortgage Bonds due August 1, 2018. Series Due June 1, 2019 [Member] Series Due June 1, 2019 [Member] Series of First Mortgage Bonds due June 1, 2019. Series Due Nov. 15, 2020 [Member] Series Due Nov. 15, 2020 [Member] Series of First Mortgage Bonds due November 15, 2020. Series Due Sept. 15, 2022 Series Due Sept. 15, 2022 [Member] Series of First Mortgage Bonds due Sept. 15, 2022. Series Due March 15, 2023 Series Due March 15, 2023 [Member] Series of First Mortgage Bonds due March 15, 2023. Series Due Sept. 1, 2037 [Member] Series Due Sept. 1, 2037 [Member] Series of First Mortgage Bonds due September 1, 2037. Series Due Aug. 1, 2038 [Member] Series Due Aug. 1, 2038 [Member] Series of First Mortgage Bonds due August 1, 2038. Series Due Aug. 15, 2041 Series Due Aug. 15, 2041 [Member] Series of First Mortgage Bonds due August 15, 2041. Series Due Sept. 15, 2042 Series Due Sept. 15, 2042 [Member] Series of First Mortgage Bonds due Sept. 15, 2042. Series Due March 15, 2043 Series Due March 15, 2043 [Member] Series of First Mortgage Bonds due March 15, 2043. Series Due Oct. 1, 2018 [Member] Series Due Oct. 1, 2018 [Member] Series of First Mortgage Bonds due October 1, 2018. Series Due Sept. 1, 2038 [Member] Series Due Sept. 1, 2038 [Member] Series of First Mortgage Bonds due September 1, 2038. Series Due Oct. 1, 2042 Series Due Oct. 1, 2042 [Member] Series of First Mortgage Bonds due Oct. 1, 2042. Senior E Due Oct. 1, 2016 [Member] Senior E Due Oct. 1, 2016 [Member] Unsecured Senior notes due October 1, 2016. Senior G Due Dec. 1, 2018 [Member] Senior G Due Dec. 1, 2018 [Member] Unsecured Senior notes due Dec. 1, 2018. Senior C and D Due Oct. 1, 2033 [Member] Senior C and D Due Oct. 1, 2033 [Member] Unsecured Senior notes due October 1, 2033. Senior F Due Oct. 1, 2036 [Member] Senior F Due Oct. 1, 2036 [Member] Unsecured Senior notes due October 1, 2036. Series Due May 9, 2016 Series Due May 9, 2016 [Member] Series of Unsecured Senior notes due May 9, 2016. Series Due April 1, 2017 [Member] Series Due April 1, 2017 [Member] Series of Unsecured Senior notes due April 1, 2017. Series Due May 15, 2020 [Member] Series Due May 15, 2020 [Member] Series of Unsecured Senior notes due May 15, 2020. Series Due July 1, 2036 [Member] Series Due July 1, 2036 [Member] Series of Unsecured Senior notes due July 1, 2036. Series Due Sept. 15, 2041 [Member] Series Due Sept. 15, 2041 [Member] Series of Unsecured Senior notes due September 15, 2041. Series Due Nov. 1, 2021 [Member] Series Due Nov. 1, 2021 [Member] Series of City of La Crosse Resource Recovery Bonds due November 1, 2021. Due Oct. 15, 2030 [Member] Due Oct. 15, 2030 [Member] Debt issued in connection with the Fort McCoy System Acquisition due October 15, 2030. Due 2014-2050 [Member] Due 2014-2050 [Member] Various Eloigne Co. Affordable Housing Project notes due 2013-2050. Schedule of Capitalization, Long-term Debt [Line Items] Schedule of Capitalization, Long-term Debt [Line Items] Debt instrument, interest rate, stated percentage (in hundredths) Debt Instrument, Interest Rate, Stated Percentage Debt instrument, maturity date Debt Instrument, Maturity Date Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum (in hundredths) Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum (in hundredths) Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum Debt Instrument, Maturity Date Range, Start Debt Instrument, Maturity Date Range, Start Debt Instrument, Maturity Date Range, End Debt Instrument, Maturity Date Range, End Common Stockholders' Equity Common Stockholders Equity [Abstract] -- None. No documentation exists for this element. -- Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares outstanding (in shares) Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Pension and Retiree Medical Obligations Pension and Retiree Medical Obligations [Member] Discloses the amount of regulatory asset arising from the difference between net periodic pension or other postemployment benefit cost, according to US GAAP, and the amount of pension or other postemployment benefit cost considered for rate-making purposes, according the actions of the regulator. Pension Costs Pension Costs [Member] Non Qualified Pension Plan Non Qualified Pension Plan [Member] Discloses the amount of regulatory asset arising from the entity's non-qualified pension plan. Recoverable Deferred Taxes on AFUDC Recorded in Plant Recoverable Deferred Taxes on AFUDC Recorded in Plant [Member] Represents the amount of rate recovery related to deferred taxes for AFUDC (Allowance for Funds Used During Construction) equity, which occurs when an entity capitalizes, as part of plant and equipment, the cost of financing construction partially by equity. Contract Valuation Adjustments Contract Valuation Adjustments [Member] Fair value adjustments pertaining to certain long-term purchased power agreements used to meet energy capacity requirements. Net AROs Asset Retirement Obligation Costs [Member] Conservation Programs Conservation Programs [Member] Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions. Environmental Remediation Costs Environmental Restoration Costs [Member] Renewable Resources and Environmental Initiatives Renewable Resources and Environmental Initiatives [Member] Government mandated renewable energy and environmental costs which are deferred as regulatory assets due to the probability that the costs will be recovered from customers in future rates or amounts collected from customers through rate recovery mechanisms intended to recover the costs of renewable resources and environmental initiatives which are deferred as a regulatory liability until costs are incurred. Depreciation Differences Depreciation Differences [Member] Differences in allowable depreciation methods or useful lives between different jurisdictions that give rise to a regulatory asset for costs that normally would be expensed. Purchased Power Agreements Purchased Power Agreements [Member] Purchased Power Agreements [Member] Losses on Reacquired Debt Loss on Reacquired Debt [Member] Nuclear Refueling Outage Costs Nuclear Refueling Outage Costs [Member] Costs of routine nuclear refueling outages deferred as a regulatory asset and amortized over the expected period between outages (generally 18-24 months). The regulatory liability represents excess revenue collections for nuclear outage costs, over the amount of amortized nuclear outage costs. This deferred accounting treatment is effective for the transition period resulting from the change in accounting. Gas Pipeline Inspection and Remediation Costs Gas Pipeline Inspection and Remediation Costs [Member] Gas pipeline inspection costs incurred that would otherwise be charged to expense. These costs are included in allowable costs for rate making purposes and future revenue will be provided to permit recovery of such incurred costs. Recoverable Purchased Natural Gas and Electric Energy Costs Deferred Fuel Costs [Member] Sherco Unit 3 Deferral Sherco Unit 3 Deferral [Member] Rate action of a regulator resulting in the deferral of costs incurred related to the replacement and repair of damaged systems at Sherco Unit 3. State Commission Adjustments State Commission Adjustments [Member] State commission adjustments, which would otherwise be charged to expense, deferred as regulatory assets based on the expected ability to recover the expense in future rates. Prairie Island EPU Prairie Island Nuclear Plant Extended Power Uprate [Member] An extended power uprate (EPU) at the Prairie Island nuclear generating plant filed with the public utility's regulatory body. Property Tax Property Tax [Member] Property taxes, which would otherwise be charged to expense, deferred as regulatory assets based on the expected ability to recover the expense in future rates. Other Regulatory Assets Other Regulatory Assets [Member] Other costs, which would otherwise be charged to expense, that are deferred as regulatory assets based on the expected ability to recover them in future rates. Regulatory Assets [Line Items] Regulatory Assets [Line Items] Regulatory Asset, Current Regulatory Assets, Current Regulatory Asset, Noncurrent Regulatory Assets, Noncurrent Regulatory asset, remaining amortization period Regulatory Noncurrent Asset, Amortization Period Regulatory asset, remaining amortization period, minimum Regulatory Asset Amortization Period, minimum The minimum amortization period for recovery of the individual regulatory asset in a schedule of regulatory assets. Regulatory asset, remaining amortization period, maximum Regulatory Asset Amortization Period, maximum The maximum amortization period for recovery of the individual regulatory asset in a schedule of regulatory assets. Regulatory Asset Regulatory Assets Past expenditures not currently earning a return Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Accumulated Benefit Obligation at Dec. 31 Defined Benefit Plan, Accumulated Benefit Obligation Change in Projected Benefit Obligation [Roll Forward] Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Obligation at Jan. 1 Defined Benefit Plan, Benefit Obligation Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Plan amendments Defined Benefit Plan, Plan Amendments Actuarial (gain) loss Defined Benefit Plan, Actuarial Gain (Loss) Benefit payments Defined Benefit Plan, Benefits Paid Obligation at Dec. 31 Change in Fair Value of Plan Assets [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Fair value of plan assets at Jan. 1 Defined Benefit Plan, Fair Value of Plan Assets Actual return (loss) on plan assets Defined Benefit Plan, Actual Return on Plan Assets Employer contributions Defined Benefit Plan, Contributions by Employer Fair value of plan assets at Dec. 31 Funded Status of Plans at Dec. 31 [Abstract] Defined Benefit Plan, Funded Status of Plan [Abstract] Funded status Defined Benefit Plan, Funded Status of Plan Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract] Defined Benefit Plan, before Adoption of FAS 158 Recognition Provisions, Net Amount Recognized [Abstract] Net loss Defined Benefit Plan, before Adoption of FAS 158 Recognition Provisions, Net (Gains) Losses, Not yet Recognized Prior service (credit) cost Defined Benefit Plan, before Adoption of FAS 158 Recognition Provisions, Net Prior Service Costs (Credits), Not yet Recognized Total Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Total Total amounts not yet recognized as components of net periodic benefit cost which has been recorded on the balance sheet based upon expected recovery in rates. Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract] Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract] Current regulatory assets Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets Amount not yet recognized as a component of net periodic benefit cost which has been recorded as current regulatory assets based upon the expected recovery in rates. Noncurrent regulatory assets Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets Amount not yet recognized as a component of net periodic benefit cost which has been recorded as noncurrent regulatory assets based upon the expected recovery in rates. Deferred income taxes Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Deferred Income Taxes Amount not yet recognized as a component of net periodic benefit cost which has been recorded as deferred income taxes based upon the expected recovery in rates. Net-of-tax accumulated other comprehensive income Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Net-Of-Tax Accumulated Other Comprehensive Income Amount not yet recognized as a component of net periodic benefit cost which has been recorded as net-of-tax accumulated other comprehensive income based upon the expected recovery in rates. Total Significant Assumptions Used to Measure Benefit Obligations [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Measurement date Defined Benefit Plan, Measurement Date Discount rate for year-end valuation (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Expected average long-term increase in compensation level (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Mortality table Mortality, Morbidity and Surrender Rate Assumption Cash Flows [Abstract] Cash Flows [Abstract] -- None. No documentation exists for this element. -- Total contributions to Xcel Energy's pension plans during the period Pension Contributions Number of pension plans to which contributions were made Defined benefit plan number of pension plans to which contributions were made Number of pension plans to which contributions were made during the period. Components of Net Periodic Benefit Cost (Credit) [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] Expected return on plan assets Defined Benefit Plan, Expected Return on Plan Assets Amortization of prior service cost (credit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of net loss Defined Benefit Plan, Amortization of Gains (Losses) Net periodic benefit cost Defined Benefit Plan Net Benefit Cost Credit Recognized Before Regulatory Adjustments The total amount of net periodic benefit cost, before regulatory adjustments, for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments, before regulatory adjustments. (Costs) credits not recognized due to effects of regulation Defined Benefit Plan Costs Credit Not Recognized Due To Effects Of Regulation The amount of (costs) credit not recognized in net periodic benefit cost as reported in the financial statements of the entity due to effects of regulation. Net benefit cost recognized for financial reporting Defined Benefit Plan, Net Periodic Benefit Cost Significant Assumptions Used to Measure Costs [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] Discount rate (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Expected average long-term increase in compensation level (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Expected average long-term rate of return on assets (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Expected average long-term rate of return on assets for next fiscal year (in hundredths) Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets For Next Fiscal Year An assumption as to the rate of return on plan assets for the next fiscal year reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. Asset Retirement Obligations [Table] Asset Retirement Obligations [Table] -- None. No documentation exists for this element. -- Asset Retirement Obligations by Class of Property [Axis] Asset Retirement Obligations by Class of Property [Axis] -- None. No documentation exists for this element. -- Asset Retirement Obligations by Class of Property [Domain] Asset Retirement Obligations by Class of Property [Domain] -- None. No documentation exists for this element. -- Electric Plant Nuclear Production Decommissioning [Member] Nuclear Plant [Member] Electric Plant Steam and Other Production Ash Containment [Member] Electric Plant Steam and Other Production Ash Containment [Member] Asset retirement obligations for steam and other production ash containment assets associated with electric plant. Electric Plant Steam and Other Production Asbestos [Member] Electric Plant Steam and Other Production Asbestos [Member] Asset retirement obligations for steam and other production asbestos assets associated with electric plant. Electric Plant Wind Production [Member] Electric Plant Wind Production [Member] Asset retirement obligations for wind production assets associated with electric plant. Electric Plant Electric Distribution [Member] Electric Distribution [Member] Electric Plant Other [Member] Electric Plant Other Sources [Member] Asset retirement obligations for other production sources assets associated with electric plant. Natural Gas Plant Gas Transmission and Distribution [Member] Natural Gas Plant Gas Transmission and Distribution [Member] Asset retirement obligations for natural gas transmission and distribution assets. Gas Gathering [Member] Gas Gathering and Processing Equipment [Member] Common and Other Property Common General Plant Asbestos [Member] Common and Other Property Common General Plant Asbestos [Member] Asset retirement obligations for common general plant asbestos assets. Common and Other Property Common Miscellaneous [Member] Common and Other Property Common Miscellaneous [Member] Common and Other Property Common Miscellaneous [Member] Asset Retirement Obligations [Line Items] Asset Retirement Obligations [Line Items] -- None. No documentation exists for this element. -- Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Beginning balance Asset Retirement Obligation Liabilities recognized Asset Retirement Obligation, Liabilities Incurred Liabilities settled Asset Retirement Obligation, Liabilities Settled Accretion Asset Retirement Obligation, Accretion Expense Revisions to prior estimates Asset Retirement Obligation, Revision of Estimate Ending balance Legally restricted assets, for purposes of funding future nuclear decommissioning Decommissioning Fund Investments, Fair Value Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] At-the-Market Program At the Market Program [Member] Program under which the entity may from time to time offer and sell shares of its common stock up to an aggregate gross sales price of $400 million through an at-the-market offering program. Series Due Aug. 15, 2022 Class of Stock [Line Items] Debt Instrument [Line Items] Maturities of Long-Term Debt [Abstract] Long Term Borrowings [Abstract] -- None. No documentation exists for this element. -- 2014 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2015 Long-term Debt, Maturities, Repayments of Principal in Year Two 2016 Long-term Debt, Maturities, Repayments of Principal in Year Three 2017 Long-term Debt, Maturities, Repayments of Principal in Year Four 2018 Long-term Debt, Maturities, Repayments of Principal in Year Five Long-Term Borrowings and Other Financing Instruments [Abstract] Debt Instruments [Abstract] Face amount Debt Instrument, Face Amount Interest rate, stated percentage (in hundredths) Maturity date Principal outstanding Long-term Debt, Gross Public Utilities, General Disclosures [Abstract] Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Regulatory Agency [Axis] Regulatory Agency [Axis] Regulatory Agency [Domain] Regulatory Agency [Domain] Colorado Public Utilities Commission (CPUC) Colorado Public Utilities Commission [Member] The Colorado Public Utilities Commission (CPUC) is an independent agency that regulates the electric and natural gas service industries in Colorado's economy. Office of Consumer Counsel Office of Consumer Counsel [Member] The Colorado Office of Consumer Counsel (OCC), a division within the Department of Regulatory Agencies (DORA), represents residential, small business and agricultural utility consumers as a class in electric, natural gas and telephone proceedings before the Public Utilities Commission (PUC). Administrative Law Judge Administrative Law Judge [Member] Judges in the Administrative Law Division provide hearing and mediation services to more than 100 state agencies and local units of governments. Administrative Law Judges preside in hearings on a broad array of matters relating to rulemaking, state licensing, utility regulation, fair campaign practices, data practices and the operation of government programs. Federal Energy Regulatory Commission (FERC) Federal Energy Regulatory Commission (FERC) [Member] The United States federal regulatory agency with jurisdiction over interstate electricity sales, wholesale electric rates, hydroelectric licensing, natural gas pricing, and oil pipeline rates. Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] 2013 Gas Rate Case Gas Rate Case 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2013 natural gas service. Gas Rate Case 2013, Gas Rates 2013 Gas Rate Case 2013, Gas Rates 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2013 natural gas service as part of the 2013 Gas Rate Case. Gas Rate Case 2013, Gas Rates 2014 Gas Rate Case 2013, Gas Rates 2014 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2014 natural gas service as part of the 2013 Gas Rate Case. Gas Rate Case 2013, Gas Rates 2015 Gas Rate Case 2013, Gas Rates 2015 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2015 natural gas service as part of the 2013 Gas Rate Case. Gas Rate Case 2013, Pipeline System Integrity Adjustment 2014 Gas Rate Case 2013, Pipeline System Integrity Adjustment 2014 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2014 pipeline system integrity adjustment (PSIA) as part of the 2013 Gas Rate Case. Gas Rate Case 2013, Pipeline System Integrity Adjustment 2015 Gas Rate Case 2013, Pipeline System Integrity Adjustment 2015 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2015 pipeline system integrity adjustment (PSIA) as part of the 2013 Gas Rate Case. Gas Rate Case 2013 Net of Pipeline System Integrity Adjustment Based on Historical Test Year Gas Rate Case 2013 Net of Pipeline System Integrity Adjustment Based on Historical Test Year [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2013 natural gas service net of the Pipeline System Integrity Adjustment (PSIA) based on a Historical Test Year (HTY). 2013 Steam Rate Case Steam Rate Case 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2013 steam service. Steam Rate Case 2013, Steam Rates 2013 Steam Rate Case 2013, Steam Rates 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2013 steam service as part of the 2013 Steam Rate Case. Steam Rate Case 2013, Steam Rates 2014 Steam Rate Case 2013, Steam Rates 2014 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2014 steam service as part of the 2013 Steam Rate Case. Steam Rate Case 2013, Steam Rates 2015 Steam Rate Case 2013, Steam Rates 2015 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2015 steam service as part of the 2013 Steam Rate Case. Annual Electric Earnings Test Annual Electric Earnings Test [Member] The earnings sharing mechanism used to apply prospective electric rate adjustments for earnings in the prior year. Smart Grid City Cost Recovery Smart Grid City Cost Recovery [Member] Rider designated to recover the capital and annual operating and maintenance (O&M) costs incurred to develop and operate SmartGridCity (SGC) as part of the 2010 electric rate case filed with the public utility's regulatory body. 2012 PSIA Report 2012 PSIA Report [Member] Cost recovery mechanism used to recover costs associated with transmission and distribution pipeline integrity management programs and other projects to replace large transmission pipelines. Demand Side Management Cost Adjustment Demand Side Management Cost Adjustment [Member] The Demand Side Management Cost Adjustment (DSMCA) clause recovers Demand Side Management (DSM), interruptible service option credit costs and performance initiatives for achieving various energy savings goals. DSM related costs are fully recovered through the combination of base rates and a DSMCA tracker mechanism. Demand Side Management Cost Adjustment, 2013 Demand Side Management Cost Adjustment, 2013 [Member] The Demand Side Management Cost Adjustment (DSMCA) clause for 2013 recovers Demand Side Management (DSM), interruptible service option credit costs and performance initiatives for achieving various energy savings goals. DSM related costs are fully recovered through the combination of base rates and a DSMCA tracker mechanism. Demand Side Management Cost Adjustment, 2014 Demand Side Management Cost Adjustment 2014 [Member] The Demand Side Management Cost Adjustment (DMSCA) clause for 2013 recovers Demand Side Management (DSM), interruptible service option credit costs and performance initiatives for achieving various energy savings goals. DSM related costs are fully recovered through the combination of base rates and a DSMCA tracker mechanism. Renewable Energy Credit Sharing Renewable Energy Credit Sharing [Member] A sharing settlement which allocates margin sharing related to renewable energy credits, approved by the applicable regulatory agency. Electric Commodity Adjustment / RESA Adjustment Electric Commodity Adjustment / RESA Adjustment [Member] Regulatory proceeding to address the proposed adjustments between ECA and RESA deferred accounts. Production Formula Rate ROE Complaint Production Formula Rate ROE Complaint [Member] Production formula rate ROE complaint filed by wholesale production customers. Transmission Formula Rate Case Transmission Formula Rate Case [Member] The formal process which industries that have the legal designation of public utility are mandated to go through in order to set the rate at which they are allowed to charge consumers for their wholesale transmission service. Settlement Allocations [Axis] Settlement Allocations [Axis] The set of entities, groups, or accounts associated with the Renewable Energy Credit (REC) sharing settlement. Settlement Allocations [Domain] Settlement Allocations [Domain] Identification of the entity, group or account participating in the Renewable Energy Credit (REC) sharing settlement. Shareholders Shareholders [Member] The shareholders of the entity participating in a sharing settlement, approved by the applicable regulatory agency. Customers Customers [Member] The customers of the entity participating in a sharing settlement, approved by the applicable regulatory agency. Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Rate Matters [Abstract] Public Utilities, Rate Matters [Abstract] Public Utilities, Requested Rate Increase (Decrease), Amount Public Utilities, Requested Rate Increase (Decrease), Amount Public Utilities, Requested Return on Equity, Percentage Public Utilities, Requested Return on Equity, Percentage Public Utilities, Requested Rate Base, Amount Public Utilities, Requested Rate Base, Amount Amount of public utility's rate base in the filing with regulatory agency on which the public utility is allowed to earn a particular rate of return. Public Utilities, Requested Equity Capital Structure, Percentage Public Utilities, Requested Equity Capital Structure, Percentage Public Utilities, Requested Rate Increase (Decrease), Amended, Amount Public Utilities, Requested Rate Increase (Decrease), Amended, Amount Public Utilities, Revenue deficiency based on a forecast test year Public Utilities, Revenue deficiency based on a forecast test year Public Utilities, Revenue deficiency based on a forecast test year Public Utilities, Approved Rate Increase (Decrease), Amount Public Utilities, Approved Rate Increase (Decrease), Amount Public Utilities, Approved Return on Equity, Percentage Public Utilities, Approved Return on Equity, Percentage Public Utilities, Approved Equity Capital Structure, Percentage Public Utilities, Approved Equity Capital Structure, Percentage Entity's Recorded Provision for Revenue Subject To Refund Entity's Recorded Provision for Revenue Subject To Refund The entity's recorded provision for revenue subject to refund. Public Utilities, Adjustment for historic test year Public Utilities, Adjustment for historic test year Public Utilities, Adjustment for historic test year Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to return on equity and capital structure adjustments Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to return on equity and capital structure adjustments Public Utilities, the adjustment to a requested rate increase (decrease) approved by third parties related to return on equity (ROE) and capital structure adjustments Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to revenue adjustments Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to revenue adjustments Public Utilities, the adjustment to a requested rate increase (decrease) approved by third parties related to revenue adjustments. Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to other costs Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to other costs Public Utilities, the adjustment to a requested rate increase (decrease) approved by third parties related to other costs. Public Utilities, Rate increase (decrease) approved by third parties excluding PSIA adjustment Public Utilities, Rate increase (decrease) approved by third parties excluding PSIA adjustment Public Utilities, the rate increase (decrease) approved by third parties excluding PSIA adjustment. Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to neutralization of PSIA - base rate transfer Public Utilities, Adjustment to requested rate increase (decrease) approved by third parties related to neutralization of PSIA - base rate transfer Public Utilities, he adjustment to a requested rate increase (decrease) approved by third parties related to neutralization of PSIA - base rate transfer. Public Utilities, Return on equity used in weather normalized earnings test Public Utilities, Return on equity used in weather normalized earnings test The return on equity used in the public utility's earnings test approved by regulatory agency in which customers and shareholders will share weather normalized earnings. Public Utilities, Refund to customers due to weather normalized earnings test Public Utilities, Refund to customers due to weather normalized earnings test Public Utilities, Refund to customers due to weather normalized earnings test Public Utilities, Estimated cost of project Public Utilities, Estimated cost of project Estimated cost of the public utility's project filed with regulatory agency. Public Utilities, Annual operating and maintenance costs associated with project Public Utilities, Annual operating and maintenance costs associated with project Annual operating and maintenance (O&M) costs associated with the public utility's project filed with regulatory agency. Public Utilities, Cost of project allowed for recovery Public Utilities, Cost of project allowed for recovery Capital cost associated with the public utility's project allowed for recovery by regulatory agency. Pretax charge for project costs Pretax charge for project costs The expense charged against earnings to eliminate the capitalized costs of projects that have been terminated during the reporting period or have been disallowed for recovery in a rate filing by a regulatory agency, which is added back to net income when calculating cash provided by (used in) operations using the indirect method. Public Utilities, Cost disallowance recommended by third parties related to capital expenditures Public Utilities, Cost disallowance recommended by third parties related to capital expenditures Public Utilities, Cost disallowance recommended by third parties related to capital expenditures. Public Utilities, Total cost disallowances recommended by third parties Public Utilities, Total cost disallowances recommended by third parties Public Utilities, total cost disallowances recommended by third parties. Public Utilities, Maximum savings goal Public Utilities, Maximum savings goal The public utility's maximum savings goal in the public utility's electric Demand Side Management (DSM) energy efficiency program. Public Utilities, Percentage of net economic benefits on which incentive is earned Public Utilities, Percentage of net economic benefits on which incentive is earned Percentage of net economic benefits on which an incentive is earned in the public utility's electric Demand Side Management (DSM) energy efficiency program. Public Utilities, Maximum annual incentive Public Utilities, Maximum annual incentive The maximum annual incentive in the public utility's electric Demand Side Management (DSM) energy efficiency program. Public Utilities, Electric demand side management budget Public Utilities, Electric demand side management budget Amount of public utility's electric demand side management (DSM) budget. Public Utilities, Gas demand side management budget Public Utilities, Gas demand side management budget Amount of public utility's natural gas demand side management (DSM) budget. Public Utilities, Demand side management costs to be collected in cost adjustment rates Public Utilities, Demand side management costs to be collected in cost adjustment rates The Demand Side Management (DSM) costs to be collected in Demand Side Management Cost Adjustment (DSMCA) rates in the public utility's electric DSM energy efficiency program. Number of parties not in agreement with settlement Number of parties not in agreement with settlement The number of parties with which a settlement was not reached in a regulatory proceeding. Public Utilities, Electric demand side management budget requested Public Utilities, Electric demand side management budget requested Public Utilities, Electric demand side management budget requested. Public Utilities, Gas demand side management budget requested Public Utilities, Gas demand side management budget requested Public Utilities, gas demand side management budget requested. Public Utilities, Initial percentage of margin associated with stand alone REC transactions Public Utilities, Initial percentage of margin associated with stand alone REC transactions The public utility's percentage of margin associated with stand-alone Renewable Energy Credit (REC) transactions which will be shared beginning in 2011 as determined by regulatory agency. Public Utilities, Ultimate percentage of margin associated with stand alone REC transactions Public Utilities, Ultimate percentage of margin associated with stand alone REC transactions The public utility's ultimate percentage of margin associated with stand-alone Renewable Energy Credit (REC) transactions which will be shared by 2014 as determined by regulatory agency. Public Utilities, Margin threshold determining percentage of margin sharing Public Utilities, Margin threshold determining percentage of margin sharing The public utility's margin threshold which determines the percentage of margin sharing related to hybrid Renewable Energy Credit (REC) trades. Margins less than $20 million on hybrid REC trades of are shared 80 percent to the customers and 20 percent to the public utility. Margins in excess of the $20 million are to be shared 90 percent to the customers and 10 percent to the public utility. Public Utilities, Percentage of margin on hybrid REC approved for first 20 million of margins Public Utilities, Percentage of margin on hybrid REC approved for first 20 million of margins The public utility's percentage of margin associated with Colorado Renewable Energy Credits (REC) approved to be shared on the first $20 million of margins on hybrid REC trades. Public Utilities, Percentage of margin on hybrid REC approved for margins in excess of 20 million Public Utilities, Percentage of margin on hybrid REC approved for margins in excess of 20 million The public utility's percentage of margin associated with Colorado Renewable Energy Credits (REC) approved to be shared in excess of $20 million of margins on hybrid REC trades. Public Utilities, Customers share of margins credited against RESA regulatory asset balance Public Utilities, Customers share of margins credited against RESA regulatory asset balance The amount of the customers' share of Renewable Energy Credit trading margins netted against the public utility's renewable energy standard adjustment (RESA) regulatory asset balance. Public Utilities, Cumulative credit against RESA regulatory asset balance Public Utilities, Cumulative credit against RESA regulatory asset balance The cumulative amount of the customers' share of Renewable Energy Credit trading margins netted against the public utility's renewable energy standard adjustment (RESA) regulatory asset balance. Proposed transfer between ECA and RESA deferred accounts Proposed transfer between ECA and RESA deferred accounts The proposed transfer between ECA and RESA deferred accounts Proposed Amortization Period For Recovery Of Deferred Costs (in months) Proposed Amortization Period For Recovery Of Deferred Costs The proposed amortization period for recovery of deferred costs transferred from the RESA deferred account to the ECA deferred account. Interest Income, Other Interest Income, Other Increase (decrease) in interest rate recommended by third parties Increase (decrease) in interest rate recommended by third parties The increase (decrease) in interest rate recommended by third parties. Recommended increase (decrease) in interest income resulting from a change in interest rates, Amount Recommended increase (decrease) in interest income resulting from a change in interest rates, Amount The recommended increase (decrease) in the amount of interest income recognized resulting from a change in interest rates. Return on equity for third parties, lower bound Return on equity for third parties, lower bound The lower bound of the return on equity allowable to public utilities to charge third party customers for providing electric service. Return on equity for third parties, upper bound Return on equity for third parties, upper bound The upper bound of the return on equity allowable to public utilities to charge third party customers for providing electric service. Public Utilities, Return on equity requested by third parties Public Utilities, Return on equity requested by third parties The public utility's rate of return on equity requested by third parties as part of a rate complaint filed with regulatory agency. Potential prospective annual revenue increase (decrease) Potential prospective annual revenue increase (decrease) The potential prospective annual revenue increase (decrease) that may result from regulatory proceedings. Public Utilities, Rate increase (decrease) requested by third parties Public Utilities, Rate increase (decrease) requested by third parties Amount of the public utility's rate increase (decrease) requested by third parties as part of a rate complaint filed with regulatory agency. Public Utilities, Return on equity requested by third parties, July 1, 2012 through Nov. 16, 2012 Public Utilities, Return on equity requested by third parties, July 1, 2012 through Nov. 16, 2012 Public Utilities, the return on equity requested by third parties to be retroactively applied to the period July 1, 2012 through Nov. 16, 2012. Public Utilities, Return on equity requested by third parties, Nov. 17, 2012 and thereafter Public Utilities, Return on equity requested by third parties, Nov. 17, 2012 and thereafter Public Utilities, the return on equity requested by third parties to be retroactively applied to the period Nov. 17, 2012 and thereafter. Balance Sheet Related Disclosures [Abstract] Public Utilities, Inventory [Table] Public Utilities, Inventory [Table] Inventory [Axis] Inventory [Axis] Inventory [Domain] Inventory [Domain] Materials and supplies Supplies [Member] Fuel Public Utilities, Inventory, Fuel [Member] Natural gas Public Utilities, Inventory, Natural Gas [Member] Public Utilities, Inventory [Line Items] Public Utilities, Inventory [Line Items] Inventories Public Utilities, Inventory Statement of Financial Position [Abstract] Assets Assets [Abstract] Current assets Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable, net Accounts Receivable, Net, Current Accrued unbilled revenues Accrued Unbilled Revenues The amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms. Inventories Inventory, Net Regulatory assets Derivative instruments Derivative Instruments and Hedges, Assets Deferred income taxes Deferred Tax Assets, Net, Current Prepayments and other Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property, plant and equipment, net Property, Plant and Equipment, Net Other assets Assets, Noncurrent [Abstract] Nuclear decommissioning fund and other investments Investments and Other Noncurrent Assets Regulatory assets Derivative instruments Derivative Instruments and Hedges, Noncurrent Other Other Assets, Noncurrent Total other assets Other Assets, Excluding Property, Plant and Equipment Sum of the carrying amounts as of the balance sheet date of all assets, excluding net property, plant and equipment, that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Total assets Assets Liabilities and Equity Liabilities and Equity [Abstract] Current liabilities Liabilities, Current [Abstract] Current portion of long-term debt Long-term Debt and Capital Lease Obligations, Current Short-term debt Short-term Debt Accounts payable Accounts Payable, Current Regulatory liabilities Regulatory Liability, Current Taxes accrued Taxes Payable, Current Accrued interest Interest Payable, Current Dividends payable Dividends Payable, Current Derivative instruments Derivative Instruments and Hedges, Liabilities Other Other Liabilities, Current Total current liabilities Liabilities, Current Deferred credits and other liabilities Liabilities, Other than Long-term Debt, Noncurrent [Abstract] Deferred income taxes Deferred Tax Assets, Net, Noncurrent Deferred investment tax credits Accumulated Deferred Investment Tax Credit Regulatory liabilities Regulatory Liability, Noncurrent Asset retirement obligations Asset Retirement Obligations, Noncurrent Derivative instruments Derivative Instruments and Hedges, Liabilities, Noncurrent Customer advances Customer Advances for Construction Pension and employee benefit obligations Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Other Other Liabilities, Noncurrent Total deferred credits and other liabilities Liabilities, Other than Long-term Debt, Noncurrent Commitments and contingencies Commitments and Contingencies Capitalization Long-term debt Long-term Debt and Capital Lease Obligations Common stock — 1,000,000,000 shares authorized of $2.50 par value; 497,971,508 and 487,959,516 shares outstanding at Dec. 31, 2013 and 2012, respectively Common Stock, Value, Issued Additional paid in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total common stockholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and equity Liabilities and Equity Operating revenues Operating income Income from continuing operations Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Earnings available to common shareholders Cash dividends declared per common share (in dollars per share) Postretirement Health Care Benefits [Abstract] Postretirement Health Care Benefits Abstract -- None. No documentation exists for this element. -- Amortization period for unrecognized accumulated postretirement benefit obligation (in years) Defined Benefit Plan Amortization Period For Unrecognized Accumulated Postretirement Benefit Obligation The period (in years) to amortize unrecognized accumulated postretirement benefit obligation due to the adoption of accounting guidance regarding other non-pension postretirement benefits on a straight-line basis. Changes in Accumulated Other Comprehensive Loss, Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reclassifications out of Accumulated Other Comprehensive Loss Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Defined Contribution Plans [Abstract] Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract] Contributions to 401(k) and other defined contribution plans Defined Contribution Plan, Cost Recognized Joint Ownership of Generation, Transmission and Gas Facilities [Abstract] -- None. No documentation exists for this element. -- Investments in Jointly Owned Generation, Transmission and Gas Facilities Schedule of Jointly Owned Utility Plants [Table Text Block] Summarized Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities by Classification of Entity [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Independent Power Producing Entities Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member] Low-Income Housing Limited Partnerships Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Purchased Power Agreements [Abstract] Purchased Power Agreements [Abstract] -- None. No documentation exists for this element. -- Generating capacity (in MW) Generating capacity under long term purchased power agreements Generating capacity under long-term purchased power agreements. Amounts Reflected in Consolidated Balance Sheets [Abstract] Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract] Current assets Variable Interest Entity Consolidated Carrying Amount Current Assets The carrying amount of the consolidated Variable Interest Entity's current assets included in the reporting entity's statement of financial position. Property, plant and equipment, net Variable Interest Entity Consolidated Carrying Amount Property Plant Equipment Net The carrying amount of the consolidated Variable Interest Entity's net property, plant and equipment included in the reporting entity's statement of financial position. Other noncurrent assets Variable Interest Entity Consolidated Carrying Amount Other Noncurrent Assets The carrying amount of the consolidated Variable Interest Entity's other noncurrent assets included in the reporting entity's statement of financial position. Total assets Variable Interest Entity, Consolidated, Carrying Amount, Assets Current liabilities Variable Interest Entity Consolidated Carrying Amount Current Liabilities The carrying amount of the consolidated Variable Interest Entity's current liabilities included in the reporting entity's statement of financial position. Mortgages and other long-term debt payable Variable Interest Entity Consolidated Carrying Amount Mortgages Other Long Term Debt Payable The carrying amount of the consolidated Variable Interest Entity's mortgages and other long-term debt payable included in the reporting entity's statement of financial position. Other noncurrent liabilities Variable Interest Entity Consolidated Carrying Amount Other Noncurrent Liabilities The carrying amount of the consolidated Variable Interest Entity's other noncurrent liabilities included in the reporting entity's statement of financial position. Total liabilities Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Nuclear Obligations [Abstract] -- None. No documentation exists for this element. -- Fuel Disposal [Abstract] Fuel Disposal Abstract -- None. No documentation exists for this element. -- Fuel disposal fee charge (in dollars per KWh) Fuel Disposal Fee Charge Fuel disposal fee associated with the Department of Energy's permanent nuclear disposal program based on a charge per KWh sold to customers from nuclear generation. Number of continuous session days in Congress before fuel disposal fee adjustment become effective unless new resolution is approved Number of continuous session days in Congress before fuel disposal fee adjustment become effective unless new resolution is approved Number of continuous session days in Congress before fuel disposal fee adjustment become effective unless new resolution is approved DOE Fuel Disposal Assessments Included In Fuel Expense DOE Fuel Disposal Assessments Included In Fuel Expense Amount paid by the entity to the Department of Energy during the period in connection with the Department of Energy's permanent nuclear disposal program. Cumulative Fuel Disposal Assessments Paid To Doe Cumulative Fuel Disposal Assessments Paid To Doe Cumulative amount paid by entity to the Department of Energy in connection with the Department of Energy's permanent nuclear disposal program. Regulatory Plant Decommissioning Recovery [Abstract] Regulatory Plant Decommissioning Recovery Abstract -- None. No documentation exists for this element. -- Number Of Years Of Extended Operation At Nuclear Plant Number Of Years Of Extended Operation At Nuclear Plant Number of years the operating license and certificate of need for spent fuel capacity was extended for the Monticello nuclear plant, expiring in 2030. Number Of Authorized Canisters Filled And Placed In Dry Cask Nuclear Storage Facility Number Of Authorized Canisters Filled And Placed In Dry Cask Nuclear Storage Facility Number of canisters authorized by the Minnesota Public Utility Commission that have been filled and placed in the Monticello dry-cask nuclear storage facility. Number Of Authorized Canisters In Dry Cask Nuclear Storage Facility Number Of Authorized Canisters In Dry Cask Nuclear Storage Facility Number of canisters authorized by the Minnesota Public Utility Commission to be placed in the Monticello dry-cask nuclear storage facility. Number of authorized casks filled and placed in dry cask nuclear storage facility Number of authorized casks filled and placed in dry cask nuclear storage facility Number of casks authorized by the Minnesota Public Utility Commission that have been filled and placed in the Prairie Island dry-cask nuclear storage facility. Number of additional authorized casks for dry cask nuclear storage facility Number of additional authorized casks for dry cask nuclear storage facility Number of additional casks authorized by the Minnesota Public Utility Commission to be placed in the Prairie Island dry-cask nuclear storage facility. Assumed annual escalation rate during operations and radiological portion of decommissioning Assumed annual escalation rate during operations and radiological portion of decommissioning Assumed rate of annual increase in decommissioning costs during operations and radiological portion of decommissioning based on periodic site-specific cost studies. Assumed annual escalation rate during independent fuel storage installation and site restoration portion of decommissioning Assumed annual escalation rate during independent fuel storage installation and site restoration portion of decommissioning Assumed rate of annual increase in decommissioning costs during independent fuel storage installation and site restoration portion of decommissioning based on periodic site-specific cost studies. Assumed after tax rate of return used to determine funding for external decommissioning trust fund, low end of range Assumed after tax rate of return used to determine funding for external decommissioning trust fund, low end of range The low end of the range of the assumed after-tax rate of return used in the annuity approach to determine funding for the external nuclear decommissioning trust fund. Assumed after tax rate of return used to determine funding for external decommissioning trust fund, high end of range Assumed after tax rate of return used to determine funding for external decommissioning trust fund, high end of range The high end of the range of the assumed after-tax rate of return used in the annuity approach to determine funding for the external nuclear decommissioning trust fund. Percentage of total obligation for decommissioning expected to be funded by external decommissioning trust fund Percentage Of Total Obligation For Decommissioning Expected To Be Funded By External Funds Percentage of total obligation for decommissioning nuclear facilities expected to be funded by external decommissioning trust fund. Number of years approved for use in decommissioning scenario (in years) Number of years approved for use in decommissioning scenario (in years) The number of years approved for use by the Minnesota Public Utility Commission in the decommissioning scenario. Approved annual accrual for decommissioning costs for next year Approved annual accrual for decommissioning costs for next year Annual accrual for decommissioning costs approved by the Minnesota Public Utility Commission for 2013 for Minnesota retail customers. Funded Status of Nuclear Decommissioning Obligation [Abstract] Funded Status of Nuclear Decommissioning Obligation [Abstract] -- None. No documentation exists for this element. -- Estimated decommissioning cost obligation from most recently approved study (2011 dollars) Estimated Decommissioning Cost Obligation From Most Recently Approved Study Estimated decommissioning cost obligation based on most recently approved periodic site-specific cost study. Effect of escalating costs (to 2013 and 2012 dollars, respectively, at 3.63/2.63 percent) Effect Of Escalating Costs To Current Year Dollars Increase in estimated decommissioning cost obligation due to the effect of escalating costs to current year dollars. Estimated decommissioning cost obligation (in current dollars) Estimated Decommissioning Cost Obligation In Current Dollars Estimated decommissioning cost obligation in current year dollars based on most recently approved periodic site-specific cost study and effect of escalating costs to current year dollars. Effect of escalating costs to payment date (3.63/2.63 percent) Effect Of Escalating Costs To Payment Date Increase in estimated decommissioning cost obligation due to the effect of escalating costs to anticipated payment date. Estimated future decommissioning costs (undiscounted) Estimated Future Decommissioning Costs Undiscounted Estimated undiscounted future decommissioning costs based on periodic site-specific cost study and effect of escalating costs to anticipated payment date. Effect of discounting obligation (using risk-free interest rate) Effect Of Discounting Obligation Using Risk Free Interest Rate Decrease in estimated decommissioning cost obligation due to discounting the obligation using a risk-free interest rate. Discounted decommissioning cost obligation Discounted decommissioning cost obligation Amount of a regulatory decommissioning obligation associated with a legal obligation that a firm incurs when it constructs or operates an asset that must eventually be withdrawn from active service. This may include operating assets such as nuclear power plants or shipping vessels. Assets held in external decommissioning trust Underfunding of external decommissioning fund compared to the discounted decommissioning obligation Discounted Decommissioning Obligation Compared To Assets Currently Held In Trust Net amount of discounted decommissioning cost obligation compared to assets held in external decommissioning trust. Annual Decommissioning Recorded As Depreciation Expense [Abstract] Annual Decommissioning Reported As Depreciation Expense [Abstract] -- None. No documentation exists for this element. -- Externally funded Nuclear Decommissioning Expense Externally Funded Nuclear decommissioning expense externally funded and reported as depreciation expense. Internally funded (including interest costs) Nuclear Decommissioning Expense Internally Funded Including Interest Costs Nuclear decommissioning expense internally funded (including interest costs) and reported as depreciation expense. Net decommissioning expense recorded Nuclear Decommissioning Expense Net Net externally funded and internally funded (including interest costs) nuclear decommissioning expense reported as depreciation expense. Balance in internally funded decommissioning account Balance in internally funded decommissioning account Balance in the internally funded decommissioning account. Public Utility Commission of Texas (PUCT) Public Utility Commission of Texas [Member] The Public Utility Commission of Texas (PUCT) is an independent agency that regulates the electric and natural gas service industries in Texas' economy. New Mexico Public Regulation Commission (NMPRC) New Mexico Public Regulation Commission [Member] The New Mexico Public Regulation Commission (NMPRC) is an independent agency that regulates the electric and natural gas service industries in New Mexico's economy. New Mexico Attorney General (NMAG) New Mexico Attorney General [Member] New Mexico Attorney General [Member] Hearing Examiner Hearing Examiner [Member] Hearing examiners are employees of federal, state, and local administrative agencies who act as judges to resolve conflicts that are within the jurisdiction of their particular agency. Electric Rate Case 2014 2014 Electric Rate Case [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2014 electric service. Electric Rate Case 2012 Electric Rate Case 2012 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2012 electric service. Electric Rate Case 2012, Settlement Rates Effective May 1, 2013 Electric Rate Case 2012, Settlement Rates Effective May 1, 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2012 electric service effective May 1, 2013 on an interim basis pending approval of a settlement agreement with the Public Utility Commission of Texas (PUCT). Electric Rate Case 2012, Settlement Rates Effective September 1, 2013 Electric Rate Case 2012, Settlement Rates Effective September 1, 2013 [Member] The formal proceeding with the public utility's regulatory body to set the rate at which they are allowed to charge consumers for their 2012 electric service effective September 1, 2013 on an interim basis pending approval of a settlement agreement with the Public Utility Commission of Texas (PUCT). Transmission Cost Recovery Factor (TCRF) Rider Transmission Cost Recovery Factor (TCRF) Rider [Member] The formal proceeding with the public utility's regulatory body to determine the costs for which they are allowed to recover transmission infrastructure improvement expenses and changes in wholesale transmission charges in Texas. Federal Energy Regulatory Commission (FERC) Orders Federal Energy Regulatory Commission (FERC) Orders [Member] Federal Energy Regulatory Commission (FERC) Orders [Member] FERC Orders, Settlement Impact Through May 31, 2015 FERC Orders, Settlement Impact Through May 31, 2015 [Member] FERC Orders, Settlement Impact Through May 31, 2015 [Member] FERC Orders, Settlement Impact Effective June 1, 2015 FERC Orders, Settlement Impact Effective June 1, 2015 [Member] FERC Orders, Settlement Impact Effective June 1, 2015 [Member] Wholesale Electric Rate Complaint Wholesale Electric Rate Complaint [Member] The formal process which third party (or parties) can go through to request the applicable regulatory agency to reconsider the rate at which industries that have the legal designation of public utility are allowed to charge consumers for their wholesale electric service. Long Lived Assets Held-for-sale by Asset Type [Axis] Long Lived Assets Held-for-sale by Asset Type [Axis] Long Lived Assets Held-for-sale, Name [Domain] Long Lived Assets Held-for-sale, Name [Domain] Sale of Texas Transmission Assets Certain Texas Transmission Assets [Member] Certain segments of SPS' transmission lines and two related substations included in the purchase and sale agreement with Sharyland Distribution and Transmission Services, LLC. Public Utilities, Requested Rate Increase (Decrease), Net Amount Public Utilities, Requested Rate Increase (Decrease), Net Amount Net amount of public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, Requested Rate Increase (Decrease), Percentage Public Utilities, Requested Rate Increase (Decrease), Percentage Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to resetting TCRF to zero Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to resetting TCRF to zero Adjustment requested by public utility to rate increase (decrease) related to resetting the transmission cost recovery factor (TCRF) rider to zero. Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to customer credit for gain on sale Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to customer credit for gain on sale Adjustment requested by public utility to rate increase (decrease) related to customer credit for gain on sale. Public Utilities, Requested base revenue increase (decrease) excluding fuel clause offsets Public Utilities, Requested base revenue increase (decrease) excluding fuel clause offsets Requested base revenue increase (decrease) excluding fuel clause offsets Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to fuel offsets Public Utilities, Adjustment requested by public utility to rate increase (decrease) related to fuel offsets Adjustment requested by public utility to rate increase (decrease) related to fuel offsets. Public Utilities, Portion of requested rate increase (decrease) related to depreciation expense Public Utilities, Portion of requested rate increase (decrease) related to depreciation expense The portion of a public utility's requested rate increase (decrease) related to depreciation expense. Public Utilities, Interim Rate Increase (Decrease), Amount Public Utilities, Interim Rate Increase (Decrease), Amount Public Utilities, Number of months included in test year for rate filing Public Utilities, Number of months included in test year for rate filing Number of months in the test year upon which the public utility's rate filing is based. Public Utilities, Requested increase (decrease) to rider revenue Public Utilities, Requested increase (decrease) to rider revenue A public utility's requested increase (decrease) to rider revenue. Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to the rate rider for renewable energy costs Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to the rate rider for renewable energy costs The adjustment to a public utility's rate request recommended by third parties related to the rate rider for renewable energy costs. Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to revenue adjustments Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to revenue adjustments Amount of adjustment requested by third parties related to revenue adjustments in the public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, Adjustment recommended by third parties related to return on equity Public Utilities, Adjustment recommended by third parties related to return on equity Public Utilities, Adjustment recommended by third parties related to return on equity Public Utilities, ROE recommended by third parties Public utilities, ROE recommended by third parties Public utilities, the ROE recommended by third parties in a rate case filing. Public Utilities, rider revenue increase (decrease) recommended by third parties Public Utilities, rider revenue increase (decrease) recommended by third parties Public Utilities, the rider revenue increase (decrease) recommended by third parties. Public Utilities, Adjustment to requested rate increase (decrease) related to change in capital structure Public utilities, adjustment to requested rate increase (decrease) related to change in capital structure Public utilities, the adjustment to a requested rate increase (decrease) recommended by third parties related to a change in capital structure Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to reduced recovery for employee benefits Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to reduced recovery for employee benefits Amount of adjustment requested by third parties related to reduced recovery for employee benefits in the public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to reduced recovery for payroll expense Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to reduced recovery for payroll expense Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to reduced recovery for payroll expense Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to gain on sale of assets Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to gain on sale of assets Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to gain on sale of assets Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to fuel clause revenue Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to fuel clause revenue Public utilities, adjustment to requested rate increase (decrease) recommended by third parties related to fuel clause revenue. Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to other costs Public Utilities, Adjustment to requested rate increase (decrease) requested by third parties related to other costs Amount of adjustment requested by third parties related to reduced recovery for other costs in the public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, Addition (reduction) to revised requested rate increase (decrease) recommended by third parties Public Utilities, Addition (reduction) to revised requested rate increase (decrease) recommended by third parties The addition (reduction) to a public utility's revised requested rate increase (decrease) recommended by third parties. Public Utilities, Rate increase (decrease) recommended by third parties Public Utilities, Rate increase (decrease) recommended by third parties Amount of the rate increase (decrease) recommended by third parties in the public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, Equity capital structure recommended by third parties Public Utilities, Equity capital structure recommended by third parties The percentage of equity to capital, including debt and equity, recommended by third parties in the public utility's requested rate increase (decrease) with regulatory agency. Public Utilities, portion of rate increase (decrease) recommended by third parties to be recovered in base revenue Public utilities, portion of rate increase (decrease) recommended by third parties to be recovered in base revenue Public utilities, the portion of rate increase (decrease) recommended by third parties to be recovered in base revenue. Public Utilities, portion of rate increase (decrease) recommended by third parties to be recovered in rider revenue Public utilities, portion of rate increase (decrease) recommended by third parties to be recovered in rider revenue Public utilities, the portion of rate increase (decrease) recommended by third parties to be recovered in rider revenue. Public Utilities, portion of rate increase (decrease) recommended by third parties to be recovered in fuel cost adjustment revenue Public utilities, portion of rate increase (decrease) recommended by third parties to be recovered in fuel cost adjustment revenue Public utilities, the portion of rate increase (decrease) recommended by third parties to be recovered in fuel cost adjustment revenue. Public Utilities, portion of revised rate increase (decrease) related to base and fuel revenue. Public utilities, portion of revised rate increase (decrease) related to base and fuel revenue. Public utilities, the portion of revised rate request with a regulatory agency related to base and fuel revenue. Public Utilities, portion of revised rate increase (decrease) related to rider revenue Public utilities, portion of revised rate increase (decrease) related to rider revenue Public utilities, the portion of revised rate increase (decrease) with a regulatory agency related to rider revenue. Public Utilities, portion of revised rate increase (decrease) related to other costs Public utilities, portion of revised rate increase (decrease) related to other costs Public utilities, the portion of revised rate increase (decrease) with regulatory agency related to other costs. Number of components included in regulatory proceeding Number of components included in regulatory proceeding The number of components included in regulatory proceeding. Number of coincident peaks used as demand allocator, revised Number of coincident peaks used as demand allocator, revised Number of coincident peaks used as demand allocator, revised Number of coincident peaks used as demand allocator, original Number of coincident peaks used as demand allocator, original Number of coincident peaks used as demand allocator, original Current year pre-tax earnings impact of regulatory proceedings Current year pre-tax earnings impact of regulatory proceedings Current year pre-tax earnings impact of regulatory proceedings Public Utilities, Annual increase (decrease) in revenues resulting from regulatory proceeding Public utilities, annual increase (decrease) in revenues resulting from regualtory proceeding Public utilities, annual increase (decrease) in revenues resulting from regualtory proceeding Public Utilities, Base return on equity charged to customers through production formula rates, Percentage Public Utilities, Base return on equity charged to customers through production formula rates, Percentage Percentage of public utility's requested base return on equity charged to customers through production formula rates filed with regulatory agency. Public Utilities, Base return on equity charged to customers through transmission formula rates, Percentage Public Utilities, Base return on equity charged to customers through transmission formula rates Percentage of public utility's requested base return on equity charged to customers through transmission formula rates filed with regulatory agency. Public Utilities, Base return on equity requested by customers, Percentage Public Utilities, Base return on equity requested by customers Percentage of public utility's requested base return on equity requested by a party (or parties) independent of the entity, as part of a rate complaint filed with regulatory agency. Public Utilities, Return on equity incentive related to transmission formula rates (in basis points) Public Utilities, return on equity incentive related to transmission formula rates Public Utilities, return on equity incentive related to transmission formula rates Number of substations included in purchase and sale agreement Number of substations included in purchase and sale agreement Number of related substations included in the purchase and sale agreement for the sale of certain segments of the entity's transmission lines. Proceeds from Sale of Property, Plant, and Equipment Proceeds from Sale of Property, Plant, and Equipment Public Utilities, Regulatory liabilities recognized for jurisdictional gain sharing Public Utilities, Regulatory liabilities recognized for jurisdictional gain sharing The amount recorded in the current year by a public utility as regulatory liabilities to be refunded to customers for jurisdictional sharing of a gain on sale of assets. Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Guarantor Obligations by Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Payment or Performance Guarantee Payment or Performance Guarantee [Member] An agreement (contract) that requires the guarantor to make payments to a guaranteed party based on another entity's failure to perform under an obligating agreement or contingently requires the guarantor to make payments (either in cash, financial instrument, other assets, shares of its stock, or provision of services) to the guaranteed party based on changes in an underlying that is related to an asset, a liability, or an equity security of the guaranteed party. Indemnification Agreement [Member] Indemnification Agreement [Member] Underlying Asset Class [Axis] Underlying Asset Class [Axis] Underlying Asset Class [Domain] Underlying Asset Class [Domain] Customer Loans for Farm Rewiring Program [Member] Loans Payable [Member] Obligations Under Aircraft Leases [Member] Obligations Under Aircraft Leases [Member] -- None. No documentation exists for this element. -- Obligations under railcar leases [Member] Obligations under railcar leases [Member] Obligations under railcar lease Surety Bonds Surety Bonds [Member] Promise to pay one party a certain amount if another party fails to meet an obligation. Obligations Under Sale Of Sharyland [Member] Obligations Under Sale Of Sharyland [Member] Obligations Under Sale Of Sharyland Guarantee Entity [Axis] Guarantee Entity [Axis] The set of legal entities receiving a guarantee, for example performance, indemnification, payment and other guarantees. Guarantee Entity [Domain] Guarantee Entity [Domain] The names of the entities receiving a guarantee, Xcel Energy Services Inc. Xcel Energy Services Inc. [Member] Xcel Energy Services Inc. is the service company for the Xcel Energy holding company. Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Guarantees [Abstract] Guarantees [Abstract]