Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-In Capital [Member] Additional Paid-in Capital [Member] Unearned Compensation ESOP [Member] Employee Stock Ownership Plan [Member] A plan where shares of company stock are allocated to qualified employees based on the proportion of their qualifying compensation to total qualifying compensation. Funds are borrowed by the ESOP from the Company to purchase the Company's common stock and repaid from the Bank's contributions and dividends paid on unallocated ESOP shares. The shares pledged as collateral are reported as a reduction of stockholders' equity at cost. As ESOP shares are committed to be released from collateral each quarter, the Company records compensation expense based on the average market price of the Company's stock during the quarter. Additionally, the shares become outstanding for earnings per share ("EPS") computations once they are committed to be released. Retained Earnings [Member] Retained Earnings [Member] AOCI [Member] AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Balance Stockholders' Equity Attributable to Parent Net income Net Income (Loss) Attributable to Parent Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax ESOP activity, net Stock Issued During Period, Value, Employee Stock Ownership Plan Restricted stock activity, net Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Repurchase of common stock Stock Repurchased During Period, Value Stock options exercised Stock Issued During Period, Value, Stock Options Exercised Cash dividends to stockholders Dividends, Cash Balance Accounting Policies [Abstract] Description of Business Nature of Operations [Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Net Presentation of Cash Flows Related to Borrowings Net Presentation of Cash Flows Related to Borrowings [Policy Text Block] Disclosure of accounting policy for net presentation of cash flows related to borrowings Securities Investment, Policy [Policy Text Block] Loans Receivable Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block] Allowance for Credit Losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Federal Home Loan Bank Stock Federal Home Loan Bank Stock [Policy Text Block] Federal Home Loan Bank Stock [Policy Text Block] Premises and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Employee Stock Ownership Plan Employee Stock Ownership Plan (ESOP), Policy [Policy Text Block] Stock-based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Borrowed Funds Borrowed Funds [Policy Text Block] Borrowed Funds [Policy Text Block] Segment Information Segment Reporting, Policy [Policy Text Block] Low Income Housing Partnerships Low Income Housing Partnerships, Policy [Policy Text Block] Disclosure of accounting policy for low income housing partnerships Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Comprehensive Income Comprehensive Income, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Interest-earning deposits Interest-bearing Deposits in Banks and Other Financial Institutions Available-for-sale securities, amortized cost Available-for-sale Securities, Amortized Cost Basis Held-to-maturity securities, estimated fair value Held-to-maturity Securities, Fair Value Loans receivable, allowance for credit losses Loans and Leases Receivable, Allowance Preferred stock, par value Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Common stock, par value Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Equity [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Loans and Leases Receivable Disclosure [Abstract] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] One- to Four-Family Segment [Member] Residential Portfolio Segment [Member] Commercial Real Estate Segment [Member] Commercial Portfolio Segment [Member] Consumer Segment [Member] Consumer Portfolio Segment [Member] Class of Financing Receivable [Axis] Class of Financing Receivable, Type [Axis] Financing Receivable, Recorded Investment, Class of Financing Receivable [Domain] Class of Financing Receivable, Type [Domain] Originated [Member] One To Four Family Loans Originated [Member] One To Four Family Loans Originated [Member] Correspondent Purchased [Member] One To Four Family Loans Correspondent Purchased [Member] Correspondent purchased loan secured by residential real estate as a single family home or a multi-unit dwelling of two to four units. Bulk Purchased [Member] One To Four Family Loans Bulk Purchased [Member] Bulk purchased loan secured by residential real estate as a single family home or a multi-unit dwelling of two to four units. Home Equity [Member] Home Equity Line of Credit [Member] Other [Member] Consumer Loan [Member] Financing Receivable, Modifications [Line Items] Financing Receivable, Modifications [Line Items] Number of Contracts Financing Receivable, Modifications, Number of Contracts Pre-Restructured Outstanding Financing Receivable, Modifications, Pre-Modification Recorded Investment Post-Restructured Outstanding Financing Receivable, Modifications, Post-Modification Recorded Investment Marketable Securities [Abstract] Amortized Cost, Estimated Fair Value, and Gross Unrealized Gains and Losses Of AFS Securities Available-for-sale Securities [Table Text Block] Amortized Cost, Estimated Fair Value, and Gross Unrealized Gains and Losses Of HTM Securities Held-to-maturity Securities [Table Text Block] Schedule Of Estimated Fair Value And Gross Unrealized Losses Of Securities In Continuous Unrealized Loss Position Unrealized Gain (Loss) on Investments [Table Text Block] Schedule Of Contractual Maturities Investments Classified by Contractual Maturity Date [Table Text Block] Schedule Of Taxable And Non-taxable Components Of Interest Income Interest Income and Interest Expense Disclosure [Table Text Block] Schedule Of Carrying Value Of Securities Pledged As Collateral Schedule Of Carrying Value Of Securities Pledged As Collateral Table Text Block Schedule Of Carrying Value Of Securities Pledged As Collateral. Statement of Comprehensive Income [Abstract] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Changes in unrealized gains (losses) on AFS securities, net of taxes of $1,595, $1,494, and $(843) Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Changes in unrealized losses on cash flow hedges, net of taxes of $226, $0, and $0 Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Financing Receivable, by Credit Quality Indicator [Domain] Internal Credit Assessment [Domain] Special Mention [Member] Special Mention [Member] Substandard [Member] Substandard [Member] Financing Receivable, Recorded Investment [Line Items] Financing Receivable, Recorded Investment [Line Items] Financing receivable, total recorded investment Loans and Leases Receivable, Net of Deferred Income Investment Holdings [Table] Investment Holdings [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] GSE Debentures [Member] US Government-sponsored Enterprises Debt Securities [Member] Trust Preferred Securities [Member] Trust Preferred Securities [Member] A collateralized debt obligation backed by a shared pool of trust preferred securities. Issuers include companies in highly regulated industries such as banks, insurance companies and regulated utilities as well as some general corporate issuers. Most are rated by one or more of the standard rating agencies. MBS [Member] Residential Mortgage Backed Securities [Member] Municipal Bonds [Member] Municipal Bonds [Member] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Estimated Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Equal to or Greater Than 12 Months, Estimated Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Equal to or Greater Than 12 Months, Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Estimated Fair Value Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Held-to-maturity Securities, Continuous Unrealized Loss Position, Equal to or Greater Than 12 Months, Estimated Fair Value Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Held-to-maturity Securities, Continuous Unrealized Loss Position, Equal to or Greater Than 12 Months, Unrealized Losses Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Share-based Compensation [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] Share-based Compensation Arrangements by Share-based Payment Award, Award Type and Plan Name [Domain] Equity Award [Domain] Stock Option Plans [Member] Stock Compensation Plan [Member] Restricted Stock Plans [Member] Restricted Stock [Member] Incentive Stock Options [Member] Incentive Stock Options [Member] Incentive Stock Options [Member] Nonqualified Stock Options [Member] Nonqualified Stock Options [Member] Nonqualified Stock Options [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2000 Stock Option Plan [Member] Two Thousand Stock Option Plan [Member] Two Thousand Stock Option Plan [Member] 2012 Equity Incentive Plan [Member] Two Thousand Twelve Equity Incentive Plan [Member] Two Thousand Twelve Equity Incentive Plan [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Shares of common stock reserved for future issuance Common Stock, Capital Shares Reserved for Future Issuance Contractual term of stock options Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Contractual Term Contractual term of stock options. Plan expiration date Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date Vesting period of options Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Options outstanding at end of year, number of options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Options outstanding at end of year, weighted average exercise price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Options outstanding at end of year, weighted average remaining contractual life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Options exercisable at end of year, number of options Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Options exercisable at end of year, weighted average exercise price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Options exercisable at end of year, weighted average remaining contractual life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Number of shares available for future grants Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Vesting period of restricted stock Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Compensation expense Allocated Share-based Compensation Expense Fair value of stock options vested during the period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, In Period, Fair Value Fair value of stock options vested during the period. Unrecognized total future compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unvested restricted stock at end of year, number of shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested restricted stock at end of year, weighted average grant date fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Unrecognized total future compensation cost, net of forfeitures Employee service share based compensation nonvested awards total compensation cost not yet recognized net of forfeitures Unrecognized cost of unvested share-based compensation awards, net of forfeitures. Fair value of restricted stock vested during the period Share based compensation arrangement by share based payment award restricted stock vested in period fair value Fair value of restricted stock that vested during the period. Unrecognized total future compensation cost weighted average recognition period Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Property, Plant and Equipment, Net [Abstract] Rental expense Operating Leases, Rent Expense, Net Income Tax Disclosure [Abstract] Federal income tax expense computed at statutory Federal rate, Amount Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Federal income tax expense computed at statutory Federal rate, Percentage Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Increases (Decreases) In Taxes Resulting From: Increases (Decreases) In Taxes Abstract Increases (Decreases) in taxes resulting from: State taxes, net of Federal tax effect, Amount Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount State taxes, net of Federal tax effect, Percentage Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Low income housing tax credits, presented net of proportional amortization in 2017, Amount Effective Income Tax Rate Reconciliation, Tax Credit, Amount Low income housing tax credits, presented net of proportional amortization in 2017, Percentage Effective Income Tax Rate Reconciliation, Tax Credit, Percent ESOP related expenses, net, Amount ESOP Related Expenses Net ESOP related expenses, net. ESOP related expenses, net, Percentage Effective Income Tax Rate ESOP Related Expenses Net Effective income tax rate ESOP related expenses, net. Other, Amount Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Other, Percentage Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Income tax expense Income Tax Expense (Benefit) Income tax expense, Percentage Effective Income Tax Rate Reconciliation, Percent 2018 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2019 Operating Leases, Future Minimum Payments, Due in Two Years 2020 Operating Leases, Future Minimum Payments, Due in Three Years 2021 Operating Leases, Future Minimum Payments, Due in Four Years 2022 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Future minimum rental commitments, total Operating Leases, Future Minimum Payments Due Schedule of Financing Receivables Past Due [Table] Schedule of Financing Receivables Past Due [Table] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] Financing Receivables, 30 to 89 Days Past Due [Member] Financing Receivables, 30 to 89 Days Past Due [Member] Financing receivables that are more than 29 days past due but fewer than 90 days past due. Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing receivable, total delinquent loans Financing Receivable, Recorded Investment, Past Due Financing receivable, current loans Financing Receivable, Recorded Investment, Current Financing receivable, total recorded investment Financing receivable, nonaccrual loans Financing Receivable, Recorded Investment, Nonaccrual Status Commitments and Contingencies Disclosure [Abstract] Commitments And Contingencies Commitments and Contingencies Disclosure [Text Block] Effective income tax rate Valuation allowance Deferred Tax Assets, Valuation Allowance Unrecognized tax benefits Unrecognized Tax Benefits Deposits and Borrowed Funds [Abstract] Deposits and Borrowed Funds [Abstract] FHLB Advances Due in 2018 Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months FHLB Advances Due in 2019 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two FHLB Advances Due in 2020 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three FHLB Advances Due in 2021 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four FHLB Advances Due in 2022 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five FHLB Advances Due Thereafter Federal Home Loan Bank, Advances, Maturities Summary, Due after Year Five FHLB Advances Amount Advances from Federal Home Loan Banks Repurchase Agreements Due in 2018 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Repurchase Agreements Due in 2019 Long-term Debt, Maturities, Repayments of Principal in Year Two Repurchase Agreements Due in 2020 Long-term Debt, Maturities, Repayments of Principal in Year Three Repurchase Agreements Due in 2021 Long-term Debt, Maturities, Repayments of Principal in Year Four Repurchase Agreements Due in 2022 Long-term Debt, Maturities, Repayments of Principal in Year Five Repurchase Agreements Due Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Repurchase Agreements Amount Secured Debt, Repurchase Agreements Certificates of Deposit Due in 2018 Time Deposit Maturities, Next Twelve Months Certificates of Deposit Due in 2019 Time Deposit Maturities, Year Two Certificates of Deposit Due in 2020 Time Deposit Maturities, Year Three Certificates of Deposit Due in 2021 Time Deposit Maturities, Year Four Certificates of Deposit Due in 2022 Time Deposit Maturities, Year Five Certificates of Deposit Due Thereafter Time Deposit Maturities, after Year Five Certificates of Deposit Amount Interest-bearing Domestic Deposit, Certificates of Deposits Selected Quarterly Financial Information [Abstract] Total interest and dividend income Interest and Dividend Income, Operating Net interest and dividend income Interest Income (Expense), Net Provision for credit losses Provision for Loan and Lease Losses Net income Basic EPS Earnings Per Share, Basic Diluted EPS Earnings Per Share, Diluted Dividends declared per share Common Stock, Dividends, Per Share, Declared Average number of basic shares outstanding Weighted Average Number of Shares Outstanding, Basic Average number of diluted shares outstanding Weighted Average Number of Shares Outstanding, Diluted Condensed Financial Information of Parent Company Only Disclosure [Abstract] Parent Company Financial Information (Parent Company Only) Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule Of Income Tax Expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Differences Between Effective Rates And Statutory Federal Income Tax Rate Computed On Income Before Income Tax Expense Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Deferred Income Tax Expense (Benefit) Results From Temporary Differences In Recognition Of Revenue And Expenses For Tax Summary of Deferred Tax Liability Not Recognized [Table Text Block] Components Of Net Deferred Income Tax Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Earnings Per Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Document And Entity Information [Abstract] Document and entity information [Abstract] Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding 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 Public Float Entity Public Float Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Earnings Per Share Reconciliation Effect On Basic Earnings Per Share [Axis] Earnings Per Share Reconciliation Effect On Basic Earnings Per Share [Axis] Earnings Per Share Reconciliation, Effect On Basic Earnings Per Share [Axis] Earnings Per Share Reconciliation Effect On Basic Earnings Per Share [Domain] Earnings Per Share Reconciliation Effect On Basic Earnings Per Share [Domain] Earnings Per Share Reconciliation Effect On Basic Earnings Per Share [Domain] Average Common Shares Outstanding [Member] Average Common Shares Outstanding [Member] Average common shares outstanding Average Committed ESOP Shares Outstanding [Member] Average Committed Employee Stock Ownership Plan Shares Outstanding [Member] Average committed employee stock ownership plan shares outstanding Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Earnings Per Share Earnings Per Share Reconciliation [Abstract] Income allocated to participating securities Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Net income available to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Total basic average common shares outstanding Effect of dilutive stock options Weighted Average Number Diluted Shares Outstanding Adjustment Total diluted average common shares outstanding Net EPS: Earnings Per Share, Basic and Diluted [Abstract] Basic Diluted Antidilutive stock options, excluded from the diluted average common shares outstanding calculation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Other Comprehensive Income Components [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Components [Domain] Other Comprehensive Income Location [Domain] Unrealized Gains (Losses) on AFS Securities [Member] Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Unrealized Gains (Losses) on Cash Flow Hedges [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Balance at October 1, 2016 Accumulated Other Comprehensive Income (Loss), Net of Tax Other comprehensive income (loss), before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent Amount reclassified from AOCI Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Balance at September 30, 2017 Originate fixed-rate Loans and Leases Receivable, Commitments, Fixed Rates Originate adjustable-rate Loans and Leases Receivable, Commitments, Variable Rates Purchase/participate fixed-rate Commitments Outstanding To Purchase Fixed Rate Commitment to purchase/participate fixed-rate loans. Purchase/participate adjustable-rate Commitments Outstanding To Purchase Adjustable Rate Commitments to purchase/participate adjustable rate loans. Commitments outstanding to originate, purchase, or participate in loans Commitments Outstanding To Originate And Purchase Loans Commitments outstanding to originate and purchase loans. Investments in Affordable Housing Projects [Abstract] Investment In affordable housing limited partnerships Investment In Affordable Housing Limited Partnerships The Bank's investment in low income housing partnerships Obligations related to investments in affordable housing limited partnerships Qualified Affordable Housing Project Investments, Commitment Affordable housing tax credits commitment, year to be paid Affordable Housing Tax Credits Commitment, Year to be Paid Proportional amortization expense, amount Amortization Method Qualified Affordable Housing Project Investments, Amortization Affordable housing tax credits, amount Affordable Housing Tax Credits and Other Tax Benefits, Amount Net income tax benefit, low income housing partnerships Net Income Tax Benefit, Low Income Housing Partnerships Amount of net income tax benefit recognized related to low income housing partnerships Impairment losses from the forfeiture or ineligibility of tax credits or other circumstances, amount Affordable Housing Project Investment, Write-down, Amount Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Traditional Banking Offices [Member] Traditional Banking Offices [Member] Traditional Banking Offices [Member] In-Store Banking Offices [Member] In Store Banking Offices [Member] In-Store Banking Offices [Member] Building [Member] Building [Member] Furniture, Fixtures And Equipment [Member] Office Equipment [Member] Leasehold Improvements [Member] Leasehold Improvements [Member] Structural Building Components [Member] Other Capitalized Property Plant and Equipment [Member] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Number of Stores Number of Stores Interest-bearing deposits held at the Federal Reserve Bank Interest Bearing Deposits Held At Federal Reserve Bank Interest Bearing Deposits Held At Federal Reserve Bank Average daily balance of required reserves at the Federal Reserve Bank Average Daily Required Reserve Balance At Federal Reserve Bank Average Daily Required Reserve Balance At Federal Reserve Bank Property, plant and equipment, estimated useful life, years Property, Plant and Equipment, Useful Life Period of service required for ESOP eligibility Period Of Service Required For Plan Eligibility Period Of Service Required For Plan Eligibility Employee age required for ESOP eligibility, years Employee Age Required For Plan Eligibility Employee age required for plan eligibility, years Number of hours required for ESOP eligibility Number Of Hours Required For Plan Eligibility Number of hours required for plan eligibility Summary of Loans Receivable Summary Of Loans Receivable By Category [Table Text Block] Tabular disclosure of the various types of loans receivable and for each the gross carrying value as of the balance sheet date. Recorded Investment in Loans, Past Due Past Due Financing Receivables [Table Text Block] Recorded Investment in Loans, Nonaccrual Schedule of Financing Receivables, Non Accrual Status [Table Text Block] Recorded Investment in Classified Loans Financing Receivable Credit Quality Indicators [Table Text Block] Weighted Average Loan-to-Value and Credit Score Information Financing Receivable Credit Quality Indicator Loan To Value And Credit Scores [Table Text Block] Financing Receivable Credit Quality Indicator Loan To Value And Credit Scores Troubled Debt Restructurings on Financing Receivables Troubled Debt Restructurings on Financing Receivables [Table Text Block] Impaired Loans by Class Impaired Financing Receivables [Table Text Block] Allowance for Credit Losses Allowance for Credit Losses on Financing Receivables [Table Text Block] Property, Plant and Equipment [Table] Land [Member] Land [Member] Building and Improvements [Member] Building and Building Improvements [Member] Furniture, Fixtures and Equipment [Member] Furniture and Fixtures [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, plant and equipment, gross Property, Plant and Equipment, Gross Accumulated depreciation, property, plant and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant and equipment, net Property, Plant and Equipment, Net Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Capitol Federal Financial Inc [Member] Parent Company [Member] ASSETS: Assets [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Investment in the Bank Investment In Bank And Parent Company Parent company investment in bank subsidiary. Note receivable - ESOP E S O P Note Receivable ESOP note receivable. Other assets Other Assets TOTAL ASSETS Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] LIABILITIES: Liabilities [Abstract] Income taxes payable, net Accrued Income Taxes, Current Accounts payable and accrued expenses Accounts Payable and Other Accrued Liabilities Deferred income tax liabilities, net Deferred Tax Liabilities, Net Total liabilities Liabilities STOCKHOLDERS' EQUITY: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $.01 par value; 100,000,000 shares authorized, no shares issued or outstanding Preferred Stock, Value, Issued Common stock, $.01 par value; 1,400,000,000 shares authorized; 138,223,835 and 137,486,172 shares issued and outstanding as of September 30, 2017 and 2016, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Unearned compensation - ESOP Unearned ESOP Shares Retained earnings Retained Earnings (Accumulated Deficit) AOCI, net of tax Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Total stockholders' equity TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value, Disclosure Item Amounts [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Amount [Member] Reported Value Measurement [Member] Estimated Fair Value [Member] Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure AFS securities Available-for-sale Securities HTM securities Loans receivable Loans Receivable, Fair Value Disclosure FHLB stock Investment in Federal Home Loan Bank Stock, Fair Value Disclosure Liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Deposits Deposits, Fair Value Disclosure FHLB borrowings Federal Home Loan Bank Borrowings, Fair Value Disclosure Repurchase agreements Securities Loaned or Sold under Agreements to Repurchase, Fair Value Disclosure Interest rate swaps Derivative Liability Regulatory Capital Requirements [Abstract] Liquidation account balance Liquidation Account The amount equal to the former mutual holding company's ownership interest in the retained earnings of the former company, as determined as of a specific date, for the benefit of certain depositors of the Bank. Capital Conservation Buffer, Annual Increase Capital Conservation Buffer, Annual Increase Amount of annual percentage increase in required capital conservation buffer above minimum risk-based capital ratios Required Capital Conservation Buffer Required Capital Conservation Buffer Amount of required capital conservation buffer above minimum risk-based capital ratios Capital Conservation Buffer, Fully Phased-In Percentage Capital Conservation Buffer, Fully Phased-In Percentage Percent above minimum risk-based capital ratios of capital conservation buffer once fully phased-in Schedule Of Borrowed Funds [Table] Schedule Of Borrowed Funds [Table] Schedule Of Borrowed Funds [Table] Leverage Strategy Tiers [Axis] Leverage Strategy Tiers [Axis] Leverage Strategy Tiers [Axis] Leverage Strategy Tiers [Domain] Leverage Strategy Tiers [Domain] Leverage Strategy Tiers [Domain] Leverage Strategy [Member] Leverage Strategy [Member] Leverage Strategy [Member] Debt, Type [Axis] Short-term Debt, Type [Axis] Debt, Type [Domain] Short-term Debt, Type [Domain] FHLB Advances [Member] Federal Home Loan Bank Advances [Member] Federal Home Loan Bank Branch [Axis] Federal Home Loan Bank Branch [Axis] Federal Home Loan Bank Branch [Domain] Federal Home Loan Bank Branch [Domain] Prepayments Of FHLB Advances [Member] Prepayments Of FHLB Advances [Member] Prepayments Of FHLB Advances [Member] New Borrowings [Member] New Borrowings [Member] New Borrowings [Member] Weighted Average [Member] Weighted Average [Member] Noninterest-bearing deposits Noninterest-bearing Deposit Liabilities, Domestic Time Deposits, $250,000 or more Time Deposits, at or Above FDIC Insurance Limit FHLB borrowings, outstanding balance Long-term Federal Home Loan Bank Advances FHLB Advances, Fixed Rate Federal Home Loan Bank, Advances, Maturities Summary, Fixed Rate FHLB Advances, Variable Rate Federal Home Loan Bank, Advances, Maturities Summary, Floating Rate FHLB line of credit, outstanding balance Long-term Line of Credit FHLB line of credit available for leverage strategy, maximum Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available Expiration date for FHLB line of credit Line of Credit Facility, Expiration Date Prepayments of fixed-rate FHLB advances Prepayments Of Federal Home Bank Advances Prepayments Of Federal Home Bank Advances New fixed-rate FHLB advances Advances From Federal Home Loan Bank, New Borrowings Advances From Federal Home Loan Bank, New Borrowings Weighted average interest rate of FHLB advances Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate Weighted average remaining term to maturity in months Weighted Average Remaining Term To Maturity In Months Weighted average remaining term to maturity in months FHLB advance prepayment penalty Prepayment Penalty On FHLB Advances Penalty paid as a result of prepaying FHLB advances. Deferred penalty is recognized in interest expense over the life of the new advances. Basis point impact of FHLB prepayment penalty FHLB Prepayment Penalty Effectively Increased Interest Rate on New Advances Impact of prepayment penalty expressed in terms of basis points relative to contractual interest rate. Interest rate swaps, notional amount Derivative Liability, Notional Amount Interest rate swaps, remaining term to maturity Derivative, Average Remaining Maturity Interest rate swaps, fair value Derivative, Fair Value, Net Interest rate swaps, amount reclassified from AOCI Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Interest rate swaps, future amount to be reclassified from AOCI Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred Interest rate swaps, amount of hedge ineffectiveness recognized Loss on Cash Flow Hedge Ineffectiveness Interest rate swaps, collateral posted Collateral Already Posted, Aggregate Fair Value FHLB borrowings threshold percentage of regulatory assets F H L B Borrowings Threshold Percentage Of Regulatory Assets FHLB Borrowings Threshold Percentage Of Regulatory Assets FHLB borrowings threshold percentage of regulatory assets, temporary increase FHLB borrowings threshold percentage of regulatory assets, temporary increase Increased FHLB borrowing limit (as a percentage of regulatory assets) as approved by the FHLB president for one year. FHLB percentage of regulatory assets Fhlb Percentage Of Regulatory Assets FHLB advances as a percentage of total assets reported to regulator. Repurchase agreements Securities Sold under Agreements to Repurchase Weighted average rate of repurchase agreements Assets Sold under Agreements to Repurchase, Interest Rate Repurchase Agreements, Description of Potential Risks Repurchase Agreements, Securities Lending Transactions, and Repurchase-to-Maturity Transactions Accounted for as Secured Borrowings, Description of Potential Risks Unadvanced home equity lines of credit Unadvanced Home Equity Lines Of Credit Unadvanced Home Equity Lines Of Credit CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Equity in excess of distribution over earnings of subsidiary Equity In Excess Of Distribution Over Undistributed Earnings Of Subsidiary Equity in excess of distribution over/(undistributed) earnings of subsidiary Depreciation of equipment Depreciation, Nonproduction Provision for deferred income taxes Deferred Income Tax Expense (Benefit) Changes in: Increase (Decrease) in Operating Capital [Abstract] Other assets Increase (Decrease) in Other Operating Assets Income taxes receivable/payable Increase Decrease Income Taxes The net change during a reporting period of income taxes payable/receivable and deferred income tax assets/liabilities. Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Net cash flows provided by operating activities Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Principal collected on notes receivable from ESOP Proceeds from Collection of Notes Receivable Net cash flows provided by investing activities Net Cash Provided by (Used in) Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Net payment from subsidiary related to restricted stock awards Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Excluding Stock Options Dividends paid Payments of Dividends Repurchase of common stock Payments for Repurchase of Common Stock Stock options exercised Proceeds from Stock Options Exercised Net cash flows used in financing activities Net Cash Provided by (Used in) Financing Activities NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Cash and Cash Equivalents, Period Increase (Decrease) CASH AND CASH EQUIVALENTS: Cash and Cash Equivalents, at Carrying Value [Abstract] Beginning of year End of year Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract] Summary Of Shares Held In The ESOP Trust Employee Stock Ownership Plan (ESOP) Disclosures [Table Text Block] Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Current, Federal Current Federal Tax Expense (Benefit) Current, State Current State and Local Tax Expense (Benefit) Current income tax expense Current Federal, State and Local, Tax Expense (Benefit) Deferred, Federal Deferred Federal Income Tax Expense (Benefit) Deferred, State Deferred State and Local Income Tax Expense (Benefit) Deferred income tax expense Deferred Federal, State and Local, Tax Expense (Benefit) Share-based Arrangements with Employees and Nonemployees [Abstract] Schedule of Employee Stock Ownership Plan (ESOP) Disclosures [Table] Schedule of Employee Stock Ownership Plan (ESOP) Disclosures [Table] Subsidiary, Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock, Name of Transaction [Domain] Sale of Stock [Domain] IPO [Member] IPO [Member] Corporate Reorganization [Member] Corporate Reorganization [Member] Corporate Reorganization [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Forecast [Member] Scenario, Forecast [Member] Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] Number of shares acquired by ESOP trust Number Shares Acquired By Employee Stock Ownership Plan Number of shares acquired by employee stock ownership plan. Number of shares acquired by ESOP post corporate reorganization Number Of Shares Acquired By Employee Stock Ownership Plan Post Corporate Reorganization Number Of Shares Acquired By Employee Stock Ownership Plan Post Corporate Reorganization ESOP loan maturity date Debt Instrument, Maturity Date Shares Held In Employee Stock Ownership Plan, Allocated Shares Held In Employee Stock Ownership Plan Allocated Number of allocated shares held by the Employee Stock Ownership Plan at balance sheet date. Allocated shares are shares that have been assigned to individual participant accounts based on a known formula. Shares Held In Employee Stock Ownership Plan, Committed-to-be-Released Employee Stock Ownership Plan (ESOP), Number of Committed-to-be-Released Shares Compensation expense related to the ESOP including dividends Employee Stock Ownership Plan ESOP Compensation Expense Including Dividends On Unallocated Shares In Excess Of Debt Service Payments Employee Stock Ownership Plan ESOP Compensation Expense Including Dividends On Unallocated Shares In Excess Of Debt Service Payments Portion of compensation expense related to the ESOP attributable to changes in Company stock price Portion Of Compensation Expense Related To ESOP Attributable To Changes In Company Stock Price Portion Of Compensation Expense Related To ESOP Attributable To Changes In Company Stock Price Dividends on unallocated ESOP shares in excess of debt service payments Employee Stock Ownership Plan (ESOP), Dividends Paid to ESOP Percentage of ESOP shares participant may diversify once age requirement is met Percentage Of Employee Stock Ownership Plan Shares Diversified Percentage of Employee Stock Ownership Plan shares diversified Required age of participant in order to diversify ESOP shares, years Age Period Of Diversified Employee Stock Ownership Plan Shares Age at which employee ESOP participants may begin to diversify their ESOP shares into other investments. Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Allowance Recorded and Not Recorded [Axis] Allowance Recorded and Not Recorded [Axis] Allowance recorded and not recorded. Allowance Recorded and not Recorded [Domain] Allowance Recorded and not Recorded [Domain] Allowance recorded and not recorded. With no related allowance recorded [Member] Allowance Not Recorded [Member] With no related allowance recorded. With an allowance recorded [Member] Allowance Recorded [Member] With a related allowance recorded. Financing Receivable, Impaired [Line Items] Financing Receivable, Impaired [Line Items] Recorded Investment, No Related Allowance Impaired Financing Receivable, with No Related Allowance, Recorded Investment Recorded Investment, Allowance Recorded Impaired Financing Receivable, with Related Allowance, Recorded Investment Recorded Investment Impaired Financing Receivable, Recorded Investment Unpaid Principal Balance, No Related Allowance Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance Unpaid Principal Balance, Allowance Recorded Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance Related ACL Impaired Financing Receivable, Related Allowance Weighted average credit score Weighted Average Credit Score Weighted Average Credit Score Weighted average LTV Weighted Average Loan To Value Ratio Weighted Average Loan To Value Ratio. Deposits and Borrowed Funds Debt Disclosure [Text Block] Fair Value Of Financial Instruments Fair Value Disclosures [Text Block] Premises And Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Cash and cash equivalents (includes interest-earning deposits of $340,748 and $267,829) Securities: Available-for-sale (AFS), at estimated fair value (amortized cost of $410,541 and $517,791) Held-to-maturity (HTM), at amortized cost (estimated fair value of $833,009 and $1,122,867) Held-to-maturity Securities Loans receivable, net (allowance for credit losses (ACL) of $8,398 and $8,540) Loans and Leases Receivable, Net Amount Federal Home Loan Bank Topeka (FHLB) stock, at cost Federal Home Loan Bank Stock Premises and equipment, net Deposits Deposits, Domestic FHLB borrowings Advance payments by borrowers for taxes and insurance Advance Payments by Borrowers for Taxes and Insurance Unearned compensation, Employee Stock Ownership Plan (ESOP) Accumulated other comprehensive income (AOCI), net of tax Schedule Of Balance Sheets Condensed Balance Sheet [Table Text Block] Schedule Of Statements Of Income Condensed Income Statement [Table Text Block] Schedule Of Statements Of Cash Flows Condensed Cash Flow Statement [Table Text Block] Changes in net unrealized gains (losses) on AFS securities, deferred income taxes Other Comprehensive Income (Loss), Available-for-sale Securities, Tax Changes in net unrealized losses on cash flow hedges, deferred income taxes Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax, Portion Attributable to Parent Taxable Interest Income, Securities, Operating, Taxable Non-taxable Interest Income, Securities, Operating, Tax Exempt Interest income on investment securities Interest and Dividend Income, Securities, Operating Cash dividends to stockholders Public unit deposits Pledged Financial Instruments, Not Separately Reported, Securities for Public Unit Deposits The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for public unit deposits, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party. Repurchase agreements Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements FRB of Kansas City Pledged Financial Instruments, Not Separately Reported, Securities for Other Debt Facilities Total securities pledged as collateral Pledged Financial Instruments, Not Separately Reported, Securities Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) [Member] Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs (Level 3) [Member] Fair Value, Inputs, Level 3 [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Loans Receivable [Member] Loans Receivable [Member] Other Real Estate Owned [Member] Other Real Estate Owned [Member] Other Real Estate Owned [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Proceeds from principal repayments Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities (Decreases) increases in net unrealized losses included in OCI Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Loans individually evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Estimated selling costs Estimated Selling Costs - Percentage Estimated Selling Costs - Percentage ACL maintained for individually evaluated impaired loans Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment OREO Other Real Estate, Foreclosed Assets, and Repossessed Assets Estimated fair value of deposits FHLB Advances Schedule of Federal Home Loan Bank, Advances, by Branch of FHLB Bank [Table Text Block] Maturity of Borrowed Funds and Certificates of Deposit Schedule of Maturities of Long-term Debt [Table Text Block] Average Recorded Investment, No Related Allowance Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment Average Recorded Investment, Allowance Recorded Impaired Financing Receivable, with Related Allowance, Average Recorded Investment Average Recorded Investment Impaired Financing Receivable, Average Recorded Investment Interest Income Recognized, No Related Allowance Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method Interest Income Recognized, Allowance Recorded Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method Interest Income Recognized Impaired Financing Receivable, Interest Income, Accrual Method Loans Receivable And Allowance For Credit Losses Financing Receivables [Text Block] Summary Of Capital And Total Risk-Based Capital Ratios Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Summary Of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Summary Of The Carrying Value Of Banking Premises And Equipment Property, Plant and Equipment [Table Text Block] Schedule Of Future Minimum Rental Commitments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Class of Financing Receivable [Domain] Construction [Member] Construction Loans [Member] Permanent [Member] Commercial Loan [Member] Loans Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Loans receivable, gross Loans and Leases Receivable, before Fees, Gross Total real estate loans LoansAndLeasesReceivableTotalRealEstateGross Total (gross) amount of real estate loans, including unamortized fees, discounts, expenses, and premiums, and undisbursed loan funds. ACL Discounts/unearned loan fees Loans and Leases Receivable, Deferred Income Premiums/deferred costs Loans And Leases Receivable Premiums Deferred Costs Loans And Leases Receivable Premiums Deferred Costs Loans receivable, net Regulatory Capital Requirements Regulatory Capital Requirements under Banking Regulations [Text Block] Employee Benefit Plans Compensation and Employee Benefit Plans [Text Block] INTEREST AND DIVIDEND INCOME: Interest and Dividend Income, Operating [Abstract] Dividend income from the Bank Dividend Income From Bank Dividend income from bank subsidiary. Interest income from other investments Other Interest and Dividend Income Total interest and dividend income INTEREST EXPENSE Interest Expense NET INTEREST AND DIVIDEND INCOME NON-INTEREST INCOME Noninterest Income, Other NON-INTEREST EXPENSE: Noninterest Expense [Abstract] Salaries and employee benefits Labor and Related Expense Regulatory and outside services Regulatory And Professional Fees Fees charged for services from professionals such as lawyers and accountants, and fees paid to regulators for conducting regulatory examinations. Other non-interest expense Other Noninterest Expense Total non-interest expense Noninterest Expense INCOME BEFORE INCOME TAX EXPENSE AND EQUITY IN EXCESS OF DISTRIBUTION OVER EARNINGS OF SUBSIDIARY Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest INCOME TAX EXPENSE INCOME BEFORE EQUITY IN EXCESS OF DISTRIBUTION OVER EARNINGS OF SUBSIDIARY Income Before Equity In Undistributed Overdistributed Earnings Of Subsidiary Income before equity in undistributed (overdistributed) earnings of subsidiary. EQUITY IN EXCESS OF DISTRIBUTION OVER EARNINGS OF SUBSIDIARY NET INCOME Income Taxes Income Tax Disclosure [Text Block] Allocated ESOP shares Employee Stock Ownership Plan (ESOP), Number of Allocated Shares Unreleased ESOP shares Employee Stock Ownership Plan (ESOP), Number of Suspense Shares Total ESOP shares Employee Stock Ownership Plan (ESOP), Shares in ESOP Fair value of unreleased ESOP shares Employee Stock Ownership Plan (ESOP), Deferred Shares, Fair Value Debt Securities [Member] Debt Securities [Member] Investment Holdings [Line Items] Investment Holdings [Line Items] Available-for-sale Securities, One year or less, Amortized Cost Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis Available-for-sale Securities, One year through five years, Amortized Cost Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis Available-for-sale Securities, Five years through ten years, Amortized Cost Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis Available-for-sale Securities, Ten years and thereafter, Amortized Cost Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Available-for-sale Securities, Amortized Cost Available-for-sale Securities, Amortized Cost Available-for-sale Securities, One year or less, Estimated Fair Value Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Available-for-sale Securities, One year through five years, Estimated Fair Value Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Available-for-sale Securities, Five years through ten years, Estimated Fair Value Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Available-for-sale Securities, Ten years and thereafter, Estimated Fair Value Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Available-for-sale Securities, Estimated Fair Value Available-for-sale Securities, Estimated Fair Value Held-to-maturity Securities, One year or less, Amortized Cost Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount Held-to-maturity Securities, One year through five years, Amortized Cost Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount Held-to-maturity Securities, Five years through ten years, Amortized Cost Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount Held-to-maturity Securities, Ten years and thereafter, Amortized Cost Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount Held-to-maturity Securities, Amortized Cost Held-to-maturity Securities, Amortized Cost Held-to-maturity Securities, One year or less, Estimated Fair Value Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value Held-to-maturity Securities, One year through five years, Estimated Fair Value Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value Held-to-maturity Securities, Five years through ten years, Estimated Fair Value Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value Held-to-maturity Securities, Ten years and thereafter, Estimated Fair Value Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value Held-to-maturity Securities, Estimated Fair Value Held-to-maturity securities, Estimated Fair Value Summary Of Quarterly Data Quarterly Financial Information [Table Text Block] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Financing Receivable, Allowance for Credit Losses [Line Items] Financing Receivable, Allowance for Credit Losses [Line Items] Beginning Balance Financing Receivable, Allowance for Credit Losses Charge-offs Financing Receivable, Allowance for Credit Losses, Write-downs Recoveries Financing Receivable, Allowance for Credit Losses, Recovery Provision for credit losses Provision for Loan, Lease, and Other Losses Ending Balance Income Statement [Abstract] Loans receivable Interest and Fee Income, Loans and Leases Mortgage-backed securities (MBS) Interest Income, Securities, Mortgage Backed Cash and cash equivalents Interest Income, Deposits with Financial Institutions FHLB stock Dividend Income, Operating Investment securities INTEREST EXPENSE: Interest Expense [Abstract] FHLB borrowings Interest Expense, Federal Home Loan Bank and Federal Reserve Bank Advances, Long-term Deposits Interest Expense, Deposits Repurchase agreements Interest Expense, Securities Sold under Agreements to Repurchase Total interest expense NET INTEREST INCOME PROVISION FOR CREDIT LOSSES NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES Interest Income (Expense), after Provision for Loan Loss NON-INTEREST INCOME: Noninterest Income [Abstract] Retail fees and charges Fees and Commissions, Depositor Accounts Income from bank-owned life insurance (BOLI) Bank Owned Life Insurance Income Other non-interest income Total non-interest income Noninterest Income Information technology and communications Communications and Information Technology Occupancy, net Occupancy, Net Deposit and loan transaction costs Deposit And Loan Transaction Costs Expense paid for miscellaneous loan fees that are not deferred, and fees related to deposit transactions, such as debit card processing, electronic banking, and ATM networks. Advertising and promotional Advertising Expense Federal insurance premium Federal Deposit Insurance Corporation Premium Expense Office supplies and related expense Supplies and Postage Expense Low income housing partnerships Low Income Housing Partnerships Non-interest expense related to low income housing partnership investments. Other non-interest expense INCOME BEFORE INCOME TAX EXPENSE INCOME TAX EXPENSE Basic earnings per share (EPS) Diluted EPS Statement of Cash Flows [Abstract] FHLB stock dividends Proceeds from sales of loans receivable held-for-sale Proceeds from Sale of Mortgage Loans Held-for-sale Amortization and accretion of premiums and discounts on securities Accretion (Amortization) of Discounts and Premiums, Investments Depreciation and amortization of premises and equipment Amortization of deferred amounts related to FHLB advances, net Amortization of Deferred Amounts Related to fhlb Advances, Net Includes amortization of deferred gains and prepayment penalties related to FHLB advances or derivatives related to FHLB advances. Common stock committed to be released for allocation - ESOP Employee Stock Ownership Plan (ESOP), Compensation Expense Stock-based compensation Share-based Compensation Other assets, net Income taxes payable/receivable Increase (Decrease) in Income Taxes Payable Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Purchase of AFS securities Payments to Acquire Available-for-sale Securities Purchase of HTM securities Payments to Acquire Held-to-maturity Securities Proceeds from calls, maturities and principal reductions of AFS securities Proceeds from calls, maturities and principal reductions of HTM securities Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Proceeds from the redemption of FHLB stock Proceeds from Sale of Federal Home Loan Bank Stock Purchase of FHLB stock Payments to Acquire Federal Home Loan Bank Stock Net increase in loans receivable Payments for (Proceeds from) Loans and Leases Purchase of premises and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from sale of other real estate owned (OREO) Proceeds from Sale of Foreclosed Assets Purchase of BOLI Payment to Acquire Life Insurance Policy, Investing Activities Proceeds from BOLI death benefit Proceeds from Life Insurance Policy Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Cash dividends paid Net change in deposits Increase (Decrease) in Deposits Proceeds from borrowings Proceeds from Federal Home Loan Bank Borrowings Repayments on borrowings Repayments of Federal Home Loan Bank Borrowings Change in advance payments by borrowers for taxes and insurance Increase (Decrease) in Advance Payments by Borrowers for Taxes and Insurance Payment of FHLB prepayment penalties Payments of Debt Restructuring Costs Excess tax benefits from stock options Excess Tax Benefit from Share-based Compensation, Financing Activities Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION: Supplemental Cash Flow Information [Abstract] Income tax payments Income Taxes Paid Interest payments Interest Paid Number of Contracts Financing Receivable, Modifications, Subsequent Default, Number of Contracts Recorded Investment Financing Receivable, Modifications, Subsequent Default, Recorded Investment Schedule Of Earnings Per Share, Basic And Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Held-to-maturity Securities [Table] Schedule of Held-to-maturity Securities [Table] Schedule of Held-to-maturity Securities [Line Items] Schedule of Held-to-maturity Securities [Line Items] Held-to-maturity Securities, Gross Unrealized Gains Held-to-maturity Securities, Accumulated Unrecognized Holding Gain Held-to-maturity Securities, Gross Unrealized Losses Held-to-maturity Securities, Accumulated Unrecognized Holding Loss Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Available-for-sale Securities, Gross Unrealized Gains Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Available-for-sale Securities, Gross Unrealized Losses Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Schedule Of Fair Value Assets Measured On A Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Low Income Housing Partnerships Affordable Housing Program [Text Block] Debt Disclosure [Abstract] Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Debt [Line Items] Short-term Debt [Line Items] FHLB advances Deferred prepayment penalty FHLB advances, outstanding balance Weighted average contractual interest rate on FHLB advances Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate at Period End Weighted average effective interest rate on FHLB advances Effective Rate FHLB Advances States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date, including the net impact of interest rate swaps and the amortization of deferred prepayment penalties Other than temporary impairments, amount Other than Temporary Impairment Losses, Investments Recorded investment in loans collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Recorded investment in loans individually evaluated for impairment Financing Receivable Individually Evaluated for Impairment, Recorded Investment The balance of financing receivables that were individually evaluated for impairment. ACL for loans collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Deferred income tax assets: Components of Deferred Tax Assets [Abstract] Salaries, deferred compensation and employee benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Benefits Low income housing partnerships Deferred Tax Assets, Investments ESOP compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits ACL Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses Other Deferred Tax Assets, Other Gross deferred income tax assets Deferred Tax Assets, Gross Valuation allowance Gross deferred income tax asset, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred income tax liabilities: Components of Deferred Tax Liabilities [Abstract] FHLB stock dividends Deferred Tax Liabilities Federal Home Loan Bank Stock Dividends Deferred income tax liabilities relating to FHLB stock dividends. Premises and equipment Deferred Tax Liabilities, Property, Plant and Equipment Unrealized gain on AFS securities Deferred Tax Liabilities, Unrealized Gains On Available-for-Sale Securities Amount of deferred tax liability attributable to taxable temporary differences from unrealized gains on available-for-sale securities. Other Deferred Tax Liabilities, Other Gross deferred income tax liabilities Deferred Tax Liabilities, Gross Net deferred tax liabilities Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Capitol Federal Savings Bank [Member] Subsidiaries [Member] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Tier 1 leverage ratio, Actual Amount Tier One Leverage Capital Tier 1 leverage ratio, Actual Ratio Tier One Leverage Capital to Average Assets Tier 1 leverage ratio, For Capital Adequacy Purposes, Amount Tier One Leverage Capital Required for Capital Adequacy Tier 1 leverage ratio, For Capital Adequacy Purposes, Ratio Tier One Leverage Capital Required for Capital Adequacy to Average Assets Tier 1 leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Tier One Leverage Capital Required to be Well Capitalized Tier 1 leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Tier One Leverage Capital Required to be Well Capitalized to Average Assets CET1 capital ratio, Actual Amount Common Equity Tier One Capital CET1 capital ratio, Actual Ratio Common Equity Tier One Capital Ratio CET1 capital ratio, For Capital Adequacy Purposes, Amount Common Equity Tier One Capital Required for Capital Adequacy CET1 capital ratio, For Capital Adequacy Purposes, Ratio Common Equity Tier 1 Capital, For Capital Adequacy Purposes, Ratio The minimum Common Equity Tier 1 Capital Ratio required for capital adequacy purposes as defined by the regulators. CET1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Common Equity Tier One Capital Required to be Well-Capitalized CET1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Common Equity Tier 1 Capital Ratio Required To Be Well Capitalized The Common Equity Tier 1 Capital Ratio required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. Tier 1 capital ratio, Actual Amount Tier One Risk Based Capital Tier 1 capital ratio, Actual Ratio Tier One Risk Based Capital to Risk Weighted Assets Tier 1 capital ratio, For Capital Adequacy Purposes, Amount Tier One Risk Based Capital Required for Capital Adequacy Tier 1 capital ratio, For Capital Adequacy Purposes, Ratio Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Tier 1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Tier One Risk Based Capital Required to be Well Capitalized Tier 1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Total capital ratio, Actual Amount Capital Total capital ratio, Actual Ratio Capital to Risk Weighted Assets Total capital ratio, For Capital Adequacy Purposes, Amount Capital Required for Capital Adequacy Total capital ratio, For Capital Adequacy Purposes, Ratio Capital Required for Capital Adequacy to Risk Weighted Assets Total capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Capital Required to be Well Capitalized Total capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Capital Required to be Well Capitalized to Risk Weighted Assets Commitments Outstanding To Originate, Purchase, Or Participate In Loans Commitments Outstanding To Originate And Purchase Loans [Table Text Block] Commitments Outstanding To Originate And Purchase Loans [Table Text Block] Other Comprehensive Income Comprehensive Income (Loss) Note [Text Block] Doubtful [Member] Doubtful [Member] Serviced loans for others, aggregate amount Aggregate amount of loans serviced for others Aggregate amount of loans serviced by the Bank for others. Escrow balances on loans serviced for others escrow balances held on loans serviced for others Escrow balances held by the Bank on loans serviced for others. Loan-to-value ratio securing commercial real estate loans, maximum Loan To Value Ratio For Securing Commercial Real Estate Loans Maximum Loan To Value Ratio For Securing Commercial Real Estate Loans Maximum Debt service coverage ratio for commercial real estate loans, minimum Debt Service Coverage Ratio For Commercial Real Estate Loans Minimum For commercial real estate loans, the minimum acceptable debt service coverage ratio. Recorded investment of loans in process of foreclosure Mortgage Loans in Process of Foreclosure, Amount Carrying value of residential OREO Real Estate Acquired Through Foreclosure Loans receivable Salaries, deferred compensation and employee benefits Deferred Income Tax Expense Benefit Salaries Deferred Compensation and Employee Benefits The change during the period in the entity's deferred tax assets and liabilities attributable to salaries, deferred compensation, and employee benefits. Low income housing partnerships Deferred Income Tax Expense Benefit Low Income Housing Partnerships The change during the period in the entity's deferred tax assets and liabilities attributable to low income housing partnerships. ACL Deferred Income Tax Expense Benefit Allowance For Credit Losses The change during the period in the entity's deferred tax assets and liabilities attributable to the allowance for credit losses. Premises and equipment Deferred Income Tax Expense Benefit Fixed Assets The change during the period in the entity's deferred tax assets and liabilities attributable to fixed assets. FHLB stock dividends Deferred Income Tax Expense Benefit FHLB Stock Dividends The change during the period in the entity's deferred tax assets and liabilities attributable to FHLB stock dividends. Capitol Federal Foundation contribution Deferred Income Tax Expense Benefit Foundation Contribution Deferred Income Tax Expense Benefit Foundation Contribution Other, net Deferred Other Tax Expense (Benefit) Deferred income tax expense Selected Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block]