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] Market measure-based Restricted Stock Units (RSUs) [Member] Market Measure-Based Restricted Stock Units (RSUs) [Member] Market Measure-Based Restricted Stock Units (RSUs) [Member] Award Feature [Axis] Award Feature [Axis] Award Feature [Axis] Award Feature [Domain] Award Feature [Domain] [Domain] for Award Feature [Axis] Nonvested Restricted Stock Units RSU [Member] Nonvested Restricted Stock Units R S U [Member] Nonvested restricted stock units RSU. Vested Restricted Stock Units RSU [Member] Vested Restricted Stock Units R S U [Member] Vested Restricted Stock Units RSU Member. Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Fair value per share on valuation date (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 Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Vest date fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract] Real Estate and Accumulated Depreciation, by Property [Table] SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, by Property [Table] Major Property Class [Axis] Major Property Class [Axis] Major Property Class [Domain] Major Property Class [Domain] Development Projects in Lease-Up [Member] Development Projects in Lease-Up [Member] Development Projects in Lease-Up [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Kilroy Realty L.P. [Member] Kilroy Realty L.P. [Member] Kilroy Realty L.P. [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Secured debt [Member] Secured Debt [Member] Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] 1550 N. El Centro Avenue, Los Angeles, CA [Member] 1550 N. El Centro Avenue, Los Angeles, CA [Member] 1550 N. El Centro Avenue, Los Angeles, CA [Member] 12100 W. Olympic Blvd., Los Angeles, CA [Member] W Olympic Boulevard Los Angeles California One [Member] 12100 W. Olympic Boulevard, Los Angeles, California [Member] 2100/2110 Colorado Ave., Santa Monica, CA [Member] Colorado Avenue, Santa Monica, California [Member] 2100 Colorado Avenue, Santa Monica, California [Member] 320 Westlake Avenue North, WA[Member] Westlake Avenue North [Member] 320 Westlake Avenue North, Washington 100 Hooper Street, San Francisco, CA [Member] Hooper Street San Francisco CA [Member] Hooper Street San Francisco CA [Member] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Office Building [Member] Office Building [Member] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Building [Member] Building [Member] Tenant Improvements [Member] Building Improvements [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Real Estate and Accumulated Depreciation [Line Items] SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] Depreciation life SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Life Used for Depreciation Property depreciable lives Property, Plant and Equipment, Useful Life Number of building units Number of Building Units Number of Building Units Initial cost, encumbrances SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation, Amount of Encumbrances Rentable square feet Net Rentable Area Debt premium Debt Instrument, Unamortized Premium Unamortized debt issuance expense Unamortized Debt Issuance Expense Aggregate cost of property for federal income tax purposes SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Federal Income Tax Basis Aggregate cost of property held in a VIE SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Held in VIE SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Held in VIE Statement of Financial Position [Abstract] ASSETS Assets [Abstract] REAL ESTATE ASSETS Real Estate Investment Property, Net [Abstract] Land and improvements Land and Land Improvements Buildings and improvements Investment Building and Building Improvements Undeveloped land and construction in progress Undeveloped Land and Construction in Progress The carrying amount of land and buildings available for development and redevelopment. Additionally, the current amount of expenditures for a real estate project that has not yet been completed. Total real estate assets held for investment Real Estate Investment Property, at Cost Accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Total real estate assets held for investment, net Real Estate Investment Property, Net CASH AND CASH EQUIVALENTS Cash and Cash Equivalents, at Carrying Value RESTRICTED CASH Restricted Cash and Cash Equivalents MARKETABLE SECURITIES Debt Securities, Trading, and Equity Securities, FV-NI CURRENT RECEIVABLES, NET Accounts Receivable, Net DEFERRED RENT RECEIVABLES, NET Deferred Rent Receivables, Net DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET Deferred Leasing Costs And Acquisition Related Intangible Assets Net This element represents (1) costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease. Those activities are: evaluating the prospective lessee's financial condition; evaluating and recording guarantees, collateral, and other security arrangements; negotiating lease terms; preparing and processing lease documents; and closing the transaction; (2) the identifiable intangible asset established upon acquisition based on a favorable difference between the terms of an acquired lease and the current market terms for that lease at the acquisition date; and (3) the amount of value allocated by a lessor (acquirer) to lease agreements which exist at acquisition of a leased property. This element is net of accumulated amortization. PREPAID EXPENSES AND OTHER ASSETS, NET Prepaid Expense and Other Assets TOTAL ASSETS Assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] LIABILITIES: Liabilities [Abstract] Secured debt, net Secured Debt Unsecured debt, net Unsecured Debt Unsecured line of credit Long-term Line of Credit Accounts payable, accrued expenses and other liabilities Accounts Payable and Accrued Liabilities Accrued dividends and distributions Dividends Payable Deferred revenue and acquisition-related intangible liabilities, net Deferred Revenue And Acquisition Related Intangible Liabilities This element represents the (1) amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP; and (2) the liability associated with the acquisition of an off-market leases when the terms of the lease are unfavorable to the market terms for the lease at the date of acquisition. Rents received in advance and tenant security deposits Advance Rent, Including Tenant Security Deposits This element represents (1) money paid in advance to the lessor to protect against damage or nonpayment by the lessee during the term of the agreement; and (2) contractual amounts paid in advance by lessees. Total liabilities Liabilities COMMITMENTS AND CONTINGENCIES Commitments and Contingencies EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Stockholders’ Equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, $.01 par value, 150,000,000 shares authorized, 100,746,988 and 98,620,333 shares issued and outstanding, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Distributions in excess of earnings Retained Earnings (Accumulated Deficit) Total stockholders’ equity Stockholders' Equity Attributable to Parent Noncontrolling Interests Noncontrolling Interest Items [Abstract] Common units of the Operating Partnership Noncontrolling Interest in Operating Partnerships Noncontrolling interests in consolidated property partnerships Noncontrolling Interest in Variable Interest Entity Total noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest TOTAL LIABILITIES AND EQUITY/CAPITAL Liabilities and Equity Earnings Per Share [Abstract] Net Income Available to Common Stockholders Per Share of the Company Earnings Per Share [Text Block] Discontinued Operations and Disposal Groups [Abstract] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal group, disposed of by sale [Member] Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Plaza Yarrow Bay Properties [Member] Plaza Yarrow Bay Properties [Member] Plaza Yarrow Bay Properties [Member] Carlsbad Oaks - Lot 7 [Member] Carlsbad Oaks - Lot 7 [Member] Carlsbad Oaks - Lot 7 [Member] Carlsbad Oaks - Lots 4 & 5 [Member] Carlsbad Oaks - Lots 4 & 5 [Member] Carlsbad Oaks - Lots 4 & 5 [Member] Carlsbad Oaks - Lot 8 [Member] Carlsbad Oaks - Lot 8 [Member] Carlsbad Oaks - Lot 8 [Member] Carlsbad Oaks - Lots 7, 4 & 5, 8 [Member] Carlsbad Oaks - Lots 7, 4 & 5, 8 [Member] Carlsbad Oaks - Lots 7, 4 & 5, 8 [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Net gain (loss) on sales of land Gains (Losses) on Sales of Investment Real Estate Gross Site Acreage (unaudited) Area of Land Sales Price Dispositions Sales Price Represents the sales price of dispositions during the reporting period. Secured debt assumed by buyers in connection with land disposition Transfer of Portfolio Loans and Leases to Held-for-sale Basis of Presentation and Significant Accounting Policies [Abstract] Basis of Presentation and Significant Accounting Policies [Abstract] Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Statement [Table] Statement [Table] Preferred Units by Name [Axis] Preferred Units by Name [Axis] Preferred Units, Class [Domain] Preferred Units, Class [Domain] Capital units [Member] Capital Units [Member] Statement [Line Items] Statement [Line Items] General partner, units issued (in units) General Partners' Capital Account, Units Issued General partner, units outstanding (in units) General Partners' Capital Account, Units Outstanding Limited partner, units issued (in units) Limited Partners' Capital Account, Units Issued Limited partner, units outstanding (in units) Limited Partners' Capital Account, Units Outstanding Award Date [Axis] Award Date [Axis] Award Date [Domain] Award Date [Domain] Shareholder Meeting Date May 21, 2015 [Member] Shareholder Meeting Date May 21, 2015 [Member] Shareholder Meeting Date May 21, 2015 [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Kilroy Realty 2006 Incentive Award Plan [Member] Kilroy Realty 2006 Incentive Award Plan [Member] Kilroy Realty 2006 Incentive Award Plan [Member] Share-based compensation arrangement by share-based payment award, number of shares requested Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Requested The maximum number of shares (or other type of equity) to be approved (usually by shareholders and board of directors) by shareholders. Share-based compensation arrangement by share-based payment award, number of shares available for grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Restricted Stock Units (RSUs) [Member] Restricted Stock Units (RSUs) [Member] Time-Based Restricted Stock Units (RSUs) [Member] Time-Based Restricted Stock Units (RSUs) [Member] Time-Based Restricted Stock Units (RSUs) [Member] Number of RSUs outstanding, beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number RSU weighted average fair value, beginning balance (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 Vested RSUs, beginning balance Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Vested, Number The number of vested or total equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. Total RSUs, beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number Weighted average fair value, vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Settled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Settled in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Settled in Period Issuance of dividend equivalents (in shares) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Issuance Of Dividend Equivalents In Period The number of restricted stock units that were issued as dividend equivalents during the period. Restricted stock units issued as dividend equivalents are vested upon issuance. Weighted average fair value, issuance of dividend equivalents (in dollars per share) Share Based Compensation Arrangements, Dividends, Weighted Average Grant Date Fair Value Share Based Compensation Arrangements, Dividends, Weighted Average Grant Date Fair Value Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Weighted average fair value, forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Canceled in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Canceled in Period Number of RSUs outstanding, ending balance (in shares) RSU weighted average fair value, ending balance (in dollars per share) Vested RSUs, ending balance Total RSUs, ending balance (in shares) 1310-1327 Chesapeake Terrace, Sunnyvale, CA , Plaza Yarrow Bay Properties, and 23925, 23975, & 24025 Park Sorrento, Calabasas, CA [Member] 1310-1327 Chesapeake Terrace, Plaza Yarrow Bay Properties, and 23925, 23975, & 24025 Park Sorrento [Member] 1310-1327 Chesapeake Terrace, Plaza Yarrow Bay Properties, and 23925, 23975, & 24025 Park Sorrento [Member] 1325-1327 Chesapeake Terrace, Sunnyvale, CA [Member] 1325-1327 Chesapeake Terrace, Sunnyvale, CA [Member] 1325-1327 Chesapeake Terrace, Sunnyvale, CA [Member] 23925, 23975, & 24025 Park Sorrento, Calabasas, CA [Member] 23925, 23975, & 24025 Park Sorrento, Calabasas, CA [Member] 23925, 23975, & 24025 Park Sorrento, Calabasas, CA [Member] 5717 Pacific Center Boulevard, San Diego, CA and Sorrento Mesa and Mission Valley Portfolio [Member] 5717 Pacific Center Boulevard, San Diego, CA and Sorrento Mesa and Mission Valley Portfolio [Member] 5717 Pacific Center Boulevard, San Diego, CA and Sorrento Mesa and Mission Valley Portfolio [Member] 5717 Pacific Center Boulevard, San Diego, CA [Member] 5717 Pacific Center Boulevard, San Diego, CA [Member] 5717 Pacific Center Boulevard, San Diego, CA [Member] Sorrento Mesa and Mission Valley Portfolio [Member] Sorrento Mesa and Mission Valley Portfolio [Member] Sorrento Mesa and Mission Valley Portfolio [Member] Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] Torrey Santa Fe Properties [Member] Torrey Santa Fe Properties [Member] Torrey Santa Fe Properties [Member] 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] 4930, 4939 & 4955 Directors Place, San Diego, CA [Member] Number of buildings Number of Real Estate Properties Proceeds from sale of property held-for-sale Proceeds from Sale of Property Held-for-sale Area of land Gains on sales of operating properties Gain (Loss) on Disposition of Property Plant Equipment Fair Value Disclosures [Abstract] Fair Value Measurements and Disclosures Fair Value Disclosures [Text Block] Equity [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, forecast [Member] Scenario, Forecast [Member] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Forward Equity Offering [Member] Forward Equity Sale [Member] Forward Equity Sale [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Series H Preferred Stock [Member] Series H Preferred Stock [Member] Series G Preferred Stock [Member] Series G Preferred Stock [Member] Common Stock [Member] Common Stock [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Issuance of Equity under ATM Program [Member] Issuance of Equity under ATM Program [Member] Issuance of Equity under ATM Program. 2014 At-The-Market Program [Member] Prior At-The-Market Program [Member] Prior At-The-Market Program [Member] 2018 At-The-Market Program [Member] 2018 At-The-Market Program [Member] 2018 At-The-Market Program [Member] Class of Stock [Line Items] Class of Stock [Line Items] Preferred stock (in shares) Preferred Stock, Shares Outstanding Preferred stock, liquidation preference per share (in dollars per share) Preferred Stock, Liquidation Preference Per Share Preferred stock liquidation preference Preferred Stock, Liquidation Preference, Value Original issuance costs of redeemed preferred units Preferred Stock Redemption Premium Stock issued (in shares) Sale of Stock, Number of Shares Issued in Transaction Common stock, value, issued Stock issued, price per share (in dollar per share) Sale of Stock, Price Per Share Common stock, shares issued (in shares) Common Stock, Shares, Issued Aggregate net proceeds after selling commissions Proceeds from Issuance of Common Stock Shares issued, price per share (in dollars per share) Shares Issued, Price Per Share Aggregate gross proceeds At Market Stock Aggregate Gross Sales Price of Common Stock At Market Stock Aggregate Gross Sales Price of Common Stock At market stock offering program remained available for issuance At Market Stock Offering Program Remained Available For Issuance At Market stock offering program remained available for issuance. Stock repurchase program, number of shares authorized to be repurchased Stock Repurchase Program, Number of Shares Authorized to be Repurchased Stock repurchase program, remaining number of shares authorized to be repurchased Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased Stock repurchased during period, shares Stock Repurchased During Period, Shares Treasury stock acquired, average cost per share Treasury Stock Acquired, Average Cost Per Share Stock repurchased during period, value Stock Repurchased During Period, Value Goodwill and Intangible Assets Disclosure [Abstract] Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net Intangible Assets Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Total Partners Capital [Member] Partners Capital [Member] Total Partners Capital Member. Partners Capital Preferred Units [Member] Partners Capital Preferred Units [Member] Partners Capital Preferred Units. Partners Capital Common Unit [Member] Partners Capital Common Unit [Member] Partners Capital Common Unit. Noncontrolling Interest In Consolidated Subsidiaries [Member] Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Partners' Capital, Including Portion Attributable to Noncontrolling Interest Beginning balance units (in units) Partners' Capital Account, Units Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Redemption of Series G & H Preferred stock Redeemable Preferred Stock Value Including Distributions In Excess Of Earnings Redeemable Preferred Stock Value Including Distributions In Excess Of Earnings Issuance of common units Partners' Capital Account, Public Sale of Units Issuance of common units (in units) Partners' Capital Account, Units, Sold in Public Offering Issuance of common units in connection with acquisition Stock Issued During Period, Value, Acquisitions Issuance of common units in connection with acquisition (in units) Stock Issued During Period, Shares, Acquisitions Issuance of share-based compensation awards Partners' Capital Account, Unit-based Compensation Non-cash amortization of share-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Exercise of stock options Partners' Capital Account, Option Exercise Exercise of stock options (in units) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Repurchase of common units and restricted stock units Partners' Capital Account, Treasury Units, Purchased Repurchase of common units and restricted stock units (in units) Partners' Capital Account, Units, Treasury Units Purchased Settlement of restricted stock units for shares of common stock Stock Issued During Period, Value, Restricted Stock Award, Gross Settlement of restricted stock units for shares of common stock (in units) Partners' Capital Account, Units, Converted Contribution by noncontrolling interest in consolidated subsidiary Noncontrolling Interest, Increase from Sale of Parent Equity Interest Distributions to noncontrolling interests in consolidated property partnerships Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Preferred dividends and distributions Dividends, Preferred Stock Distributions declared per common unit General Partners' Capital Account, Period Distribution Amount Ending balance Ending balance units (in units) Allocated share-based compensation expense Allocated Share-based Compensation Expense Share-based compensation costs Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Unrecognized compensation costs Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Cost not yet recognized, period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Chief Executive Officer [Member] Chief Executive Officer [Member] Cash retirement benefit, scenario one Compensation Arrangement with Individual, Recorded Liability, Scenario One Compensation Arrangement with Individual, Recorded Liability, Scenario One Cash retirement benefit, scenario two Compensation Arrangement with Individual, Recorded Liability, Scenario Two Compensation Arrangement with Individual, Recorded Liability, Scenario Two Compensation expense Compensation Expense, Excluding Cost of Good and Service Sold Tax Treatment of Distributions [Abstract] Tax Treatment of Distributions [Abstract] Income Tax Treatment of Dividends Paid [Table] Income Tax Treatment of Dividends Paid [Table] Schedule of income tax treatment for the dividends paid to common and preferred stockholders. Component of Dividends Paid, Tax Treatment [Axis] Component of Dividends Paid, Tax Treatment [Axis] Component of Dividends Paid, Tax Treatment [Domain] Component of Dividends Paid, Tax Treatment [Domain] Tax treatment, Ordinary income [Member] Tax Treatment, Ordinary Income [Member] Tax Treatment, Ordinary Income [Member] Tax treatment, Qualified dividend [Member] Tax Treatment, Qualified Dividend [Member] Tax Treatment, Qualified Dividend [Member] Tax treatment, Return of capital [Member] Tax Treatment, Return of Capital [Member] Tax Treatment, Return of Capital [Member] Tax treatment, Capital gains [Member] Tax Treatment, Capital Gains [Member] Tax Treatment, Capital Gains [Member] Tax treatment, Unrecaptured section 1250 gains [Member] Tax Treatment, Unrecaptured Section 1250 Gains [Member] Tax Treatment, Unrecaptured Section 1250 Gains [Member] Tax treatment [Member] Tax Treatment [Member] Tax Treatment [Member] Income Tax Treatment of Dividends Paid [Line Items] Income Tax Treatment of Dividends Paid [Line Items] Dividends paid per common share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Dividends paid per common share, percentage Common Stock, Dividends_per_share, Cash Paid, Percentage The percentage of the aggregate dividends paid during the period for each share of common stock outstanding. Capital gains, federal statutory tax rate Capital Gains, Federal Statutory Tax Rate, Percent The percentage rate at which capital gains are taxed. Preferred stock, dividend rate Preferred Stock, Dividend Rate, Percentage Dividends paid per preferred share (in dollars per share) Preferred Stock, Dividends, Per Share, Cash Paid Dividend paid per preferred share, percentage Preferred Stock, Dividends_per_share, Cash Paid, Percentage The percentage of the aggregate dividends paid during the period for each share of preferred stock outstanding. Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving credit facility [Member] Revolving Credit Facility [Member] Line of credit [Member] Line of Credit [Member] Unsecured senior notes [Member] Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt balance and significant terms Schedule of Debt [Table Text Block] Schedule of unsecured revolving credit facility Schedule of Line of Credit Facilities [Table Text Block] Schedule of term loan facility Schedule of Term Loan Facilities [Table Text Block] Schedule of Term Loan Facilities [Table Text Block] Stated debt maturities and scheduled amortization payments, excluding debt discounts Schedule of Maturities of Long-term Debt [Table Text Block] Capitalized interest and loan fees Capitalized Interest And Loan Fees [Table Text Block] Capitalized interest and loan fees. Noncontrolling Interest [Abstract] Noncontrolling Interest [Table] Noncontrolling Interest [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Consolidated property partnerships [Member] Consolidated Property Partnerships [Member] Consolidated Property Partnerships [Member] Norges Bank Real Estate Management (NBREM) [Member] Norges Bank Real Estate Management (NBREM) [Member] Norges Bank Real Estate Management (NBREM) [Member] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Real estate investments, joint ventures Real Estate Investments, Joint Ventures Other ownership interests, contributed capital Other Ownership Interests, Contributed Capital Company owned general partnership interest Noncontrolling Interest, Ownership Percentage by Parent Other ownership interests, mortgage debt Other Ownership Interests, Mortgage Debt Other Ownership Interests, Mortgage Debt Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization and Ownership Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Leases [Abstract] Future Minimum Rent Lessor, Operating Leases [Text Block] Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Tenant One [Member] Tenant One [Member] Tenant One [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Provision for bad debts Provision for Doubtful Accounts Number of tenants Number Of Tenants Number of Tenants. Provisions for bad debts, increase (decrease) Allowance for Doubtful Accounts Receivable, Period Increase (Decrease) Summary of identified deferred leasing costs and acquisition-related intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Amortization for the period related to deferred leasing costs and acquisition-related intangibles Schedule Of Finite Lived Intangible Assets and Liabilities Amortization Expense [Table Text Block] Tabular disclosure of the amount of finite-lived intangible assets and liabilities amortization by major class recognized as expense during the period. Estimated annual amortization related to deferred leasing costs and acquisition-related intangibles Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Supplemental Cash Flow Elements [Abstract] SUPPLEMENTAL CASH FLOWS INFORMATION: Supplemental Cash Flow Information [Abstract] Cash paid for interest, net of capitalized interest of $65,627, $44,757, and $47,675 as of December 31, 2018, 2017 and 2016, respectively Interest Paid, Excluding Capitalized Interest, Operating Activities Capitalized interest Interest Paid, Capitalized, Investing Activities NON-CASH INVESTING TRANSACTIONS: Noncash Investing Activities [Abstract] Noncash Investing Activities. Accrual for expenditures for operating properties and development and redevelopment properties Capital Expenditures Incurred but Not yet Paid Tenant improvements funded directly by tenants Tenant improvements funded directly by tenants to third parties The amount of cash paid directly to third parties by tenants for tenant improvements owned by the Company. Assumption of other assets and liabilities in connection with operating and development property acquisitions, net Noncash or Part Noncash Acquisition, Other Liabilities Assumed Accrual for receivable related to development properties Notes Assumed NON-CASH FINANCING TRANSACTIONS: Noncash Financing Activities [Abstract] Accrual of dividends and distributions payable to common stockholders and common unitholders Common Stockholders And Unitholders Dividends And Distributions Declared But Not Paid Dividends and distributions declared but not paid to common stockholders and common unitholders. Exchange of common units of the Operating Partnership into shares of the Company’s common stock Conversion of Stock, Amount Converted Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders Preferred Stockholders And Unitholders Dividends And Distributions Declared But Not Paid Dividends and distributions declared but not paid to preferred stockholders and preferred unitholders. Issuance of common units of the Operating Partnership in connection with an acquisition Stock Issued Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets and Liabilities by Major Class [Axis] Finite-Lived Intangible Assets and Liabilities by Major Class [Axis] Information by major type or class of finite-lived intangible assets and liabilities. Finite Lived Intangible Assets Liabilities Major Class Name [Domain] Finite Lived Intangible Assets Liabilities Major Class Name [Domain] The major class of finite-lived intangible assets and liabilities. Deferred leasing costs [Member] Deferred Leasing Costs [Member] This element represents the costs incurred in connection with successful property leasing and consists primarily of leasing commissions, and also includes certain internal payroll costs and lease incentives. Above market leases [Member] Above Market Leases [Member] In-place leases [Member] Leases, Acquired-in-Place [Member] Below-Market Ground Lease Obligation [Member] Leases Acquired In Place Below Market Ground Lease Adjustment [Member] Leases Acquired In Place Below Market Ground Lease Adjustment [Member] Below Market Operating Lease [Member] Below Market Lease [Member] Below Market Leases Above-Market Ground Lease Obligation [Member] Leases Acquired In Place Above Market Ground Leases Adjustment Member Leases acquired in place above market ground leases adjustment. Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Amortization for the period related to deferred leasing costs and acquisition-related intangibles Amortization of Deferred Charges [Abstract] Amortization for the period related to deferred leasing costs and acquisition-related intangibles Amortization of Intangible Assets Amortization Of Intangible Liabilities Amortization Of Intangible Liabilities The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. Estimated annual amortization related to acquisition-related intangible assets Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-lived intangible assets, 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Finite-lived intangible assets, 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Two Finite-lived intangible assets, 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Three Finite-lived intangible assets, 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Four Finite-lived intangible assets, 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Five Finite-lived intangible assets, thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Finite-lived intangible assets Finite-Lived Intangible Assets, Net Estimated annual amortization related to acquisition-related intangible liabilities Finite-Lived Intangible Liabilities, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-Lived Intangible Liabilities, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Acquisition-related intangible liabilities, 2019 Finite Lived Intangible Liabilities Amortization Expense, Next Rolling Twelve Months Finite Lived Intangible Liabilities Amortization Expense, Next Rolling Twelve Months Acquisition-related intangible liabilities, 2020 FiniteLivedIntangibleLiabilitiesAmortizationExpenseYearTwo Amount of amortization expense expected to be recognized during the second fiscal year following the latest fiscal year for intangible liabilities with a finite life. Acquisition-related intangible liabilities, 2021 FiniteLivedIntangibleLiabilitiesAmortizationExpenseYearThree Amount of amortization expense expected to be recognized during the third fiscal year following the latest fiscal year for intangible liabilities with a finite life. Acquisition-related intangible liabilities, 2022 FiniteLivedIntangibleLiabilitiesAmortizationExpenseYearFour Amount of amortization expense expected to be recognized during the fourth fiscal year following the latest fiscal year for intangible liabilities with a finite life. Acquisition-related intangible liabilities, 2023 FiniteLivedIntangibleLiabilitiesAmortizationExpenseYearFive Amount of amortization expense expected to be recognized during the fifth fiscal year following the latest fiscal year for intangible liabilities with a finite life. Acquisition-related intangible liabilities, thereafter FiniteLivedIntangibleLiabilitiesAmortizationExpenseAfterYearFive Amount of amortization expense expected to be recognized after the fifth fiscal year following the latest fiscal year for intangible liabilities with a finite life. Acquisition-related intangible liabilities FiniteLivedIntangibleLiabilitiesNet Amount after amortization of intangible liabilities witth a finite life. Partners' Capital [Abstract] Partners' Capital of the Operating Partnership Partners' Capital Notes Disclosure [Text Block] Schedule of real estate properties Schedule of Real Estate Properties [Table Text Block] SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward] Total real estate held for investment, beginning of year Acquisitions SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Other Acquisition Improvements, etc. SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Improvements Total additions during period SEC Schedule III, Real Estate, Period Increase Total increase in the carrying amount of real estate investments during the period. Cost of real estate sold SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Cost of Investment in Real Estate Sold Properties held for sale SEC Schedule III, Real Estate, Deductions, Properties Held for Sale Total decrease in the carrying amount of real estate investments during the period due to assets held for sale. Other SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Other Deduction Total deductions during period SEC Schedule III, Real Estate, Period Decrease Total decrease in the carrying amount of real estate investments during the period. Total real estate held for investment, end of year Earnings Per Unit [Abstract] Net Income Available To Common Unitholders [Table] Net Income Available To Common Unitholders [Table] Net Income Available to Common Unitholders. Net Income Available To Common Unitholders [Line Items] Net Income Available To Common Unitholders [Line Items] Net Income Available To Common Unitholders. Net income (loss) available to common unitholders Net Loss Income Available To Common Unitholders Abstract Net (loss) income available to common unitholders. Numerator: Basic and diluted net loss income available to common unitholders [Abstract] Basic and diluted net (loss) income available to common unitholders. Net income attributable to Kilroy Realty, L.P. Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Preferred dividends and distributions Preferred Stock Dividends and Other Adjustments Allocation to participating securities (1) Participating Securities, Distributed and Undistributed Earnings (Loss), Basic Numerator for basic and diluted net income available to common stockholders Net Income (Loss) Available to Common Stockholders, Basic and Diluted Net income (loss) after adjustments for preferred distributions and dividends and allocations to participating securities. Denominator: Earnings Per Common Unit, Denominator [Abstract] Earnings Per Common Unit - Denominator Basic weighted average vested shares/units outstanding (in shares/units) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive securities (in units) Weighted Average Number Diluted Shares Outstanding Adjustment Diluted weighted average vested shares and common stock/ unit equivalents outstanding (in shares/units) Weighted Average Number of Shares Outstanding, Diluted Basic earnings per unit: Earnings Per Unit Basic Abstract Earnings Per Unit Basic. Net income available to common unitholders per unit (in dollars per unit) Earnings Per Share, Basic Diluted earnings per unit: Earnings Per Unit Diluted Abstract Earnings Per Unit Diluted Abstract. Net income available to common unitholders per unit (in dollars per unit) Earnings Per Share, Diluted Commitments and Contingencies Disclosure [Abstract] Long-term Purchase Commitment [Table] Long-term Purchase Commitment [Table] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Domain] Environmental Remediation Contingency [Domain] Environmental matters [Member] Environmental Matters [Member] Environmental Matters [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Property damage litigation case [Member] Property Damage Litigation Case [Member] Property Damage Litigation Case [Member] Lease Extension Options [Axis] Lease Extension Options [Axis] Lease Extension Options [Axis] Lease Extension Options [Domain] Lease Extension Options [Domain] Lease Extension Options [Domain] Ten year ground lease extension option [Member] Ten Year Ground Lease Extension Option [Member] Ten Year Ground Lease Extension Option [Member] Forty-five year ground lease extension option [Member] Forty-Five Year Ground Lease Extension Option [Member] Forty-Five Year Ground Lease Extension Option [Member] Long-term Purchase Commitment [Line Items] Long-term Purchase Commitment [Line Items] Commitments for contracts and executed leases, operating and redevelopment and development properties Other Commitment Number of extension options Number of Ground Lease Extension Options Number of extension options on ground lease. Ground lease extension option term Ground Lease Extension Option, Period Ground Lease Extension Option, Period Period after which ground lease rentals are adjusted based on fair market value and the Consumer Price Index Period for Ground lease rentals adjustment Period for Ground lease rentals adjustment. Annual ground lease rental obligations limit Annual Ground Lease Rental Obligations, Maximum Maximum annual ground lease rental obligations. Duration of ground lease prior to increase five years Ground Lease, Minimum Rent Increase, Period of Increase Ground Lease, Minimum Rent Increase, Period of Increase Average annual percentage rent for previous five years (percent) Ground Lease, Minimum Rent Increase, Percentage of Annual Percentage Rent Ground Lease, Minimum Rent Increase, Percentage of Annual Percentage Rent for the previous 5 years Duration of ground lease prior to increase ten years Ground Lease, Minimum Rent Increase, Period of Increase Two Ground Lease, Minimum Rent Increase, Period of Increase Two Average annual percentage rent for previous ten years (percent) Ground Lease, Minimum Rent Increase, Percentage of Annual Percentage Rent Two Ground Lease, Minimum Rent Increase, Percentage of Annual Percentage Rent Two Accrued environmental remediation liabilities Accrual for Environmental Loss Contingencies Proceeds from legal settlements Proceeds from Legal Settlements Tax Treatment of Distributions Tax Treatment of Distributions [Text Block] Tax Treatment of Distributions [Text Block] Deferred Revenue Disclosure [Abstract] Deferred revenue and acquisition-related liabilities Deferred revenue and acquisition-related liabilities disclosure [Table Text Block] Tabular disclosure of the deferred revenue and acquisition-related liabilities balances as of the balance sheet date. Estimated amortization of deferred revenue related to tenant-funded improvements Schedule of Future Amortization of Deferred Revenue Related to Tenant-Funded Tenant Improvements [Table Text Block] Tabular disclosure of the future amortization of deferred revenue related to tenant-funded improvements for the next five years and thereafter [Table Text Block] Retirement Benefits [Abstract] Eligibility period for 401K savings plan, period Defined Contribution Plan, Requisite Service Period The number of months of service required before an employee is eligible to participate in the Company's 401(k) Plan. 401(k) plan, maximum participant deferral percent Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent 401(k) plan, employer match per dollar of participant contribution Defined Contribution Plan, Employer Matching Contribution Per Participant Dollar The amount of each one dollar that the Company will contribute to an employees benefit plan up to a set percentage of their base salary. 401(k) plan, maximum employer match percentage Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay 401(k) plan, contributions made Defined Contribution Plan, Cost Deferred Compensation, maximum participant deferral percent Deferred Compensation, Employee Salary, Percent The maximum percentage of certain management employees annual salaries that can be deferred. Deferred Compensation, maximum director fees and bonuses that may be deferred (percent) Deferred Compensation, Directors Fees and Employee Bonuses, Percent The maximum percentage of directors and certain management employees bonuses and directors fees which may be deferred. Deferred Compensation, mandatory Company contributions as percentage of gross monthly salary (percent) Deferred Compensation Arrangement with Individual, Employer Contribution, Percent The percentage of an employee's gross monthly salary for which mandatory Company contributions will be made to the employee, without regard as to whether such employee elects to defer salary or bonus compensation under the Deferred Compensation Plan. Deferred Compensation, liability under Plan Deferred Compensation Liability, Current and Noncurrent Line of Credit Facility [Table] Line of Credit Facility [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] London Interbank Offered Rate (LIBOR) [Member] London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] $150.0 million term loan facility [Member] One Hundred Fifty Million Term Loan Facility [Member] One Hundred Fifty Million Term Loan Facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Terms of the Credit Facility Line of Credit Facility [Abstract] Outstanding borrowings Remaining borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Total borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Interest rate Line of Credit Facility, Interest Rate at Period End Facility fee-annual rate Line of Credit Facility, Commitment Fee Percentage Undrawn facility fee-annual rate Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Maturity date Line of Credit Facility, Expiration Date Contingent additional borrowings Debt Instrument, Contingent Additional Borrowings Debt Instrument, Contingent Additional Borrowings Basis spread on LIBOR Debt Instrument, Basis Spread on Variable Rate Line of credit facility, increase (decrease) Line of Credit Facility, Increase (Decrease), Net Borrowings on unsecured debt Proceeds from Unsecured Notes Payable Quarterly Financial Information Disclosure [Abstract] Revenues Revenues Net income attributable to Kilroy Realty Corporation Net Income (Loss) Attributable to Parent Net income available to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Net income available to common stockholders per share/ unit—basic (dollars per share/ unit) Net income available to common stockholders per share/ unit—diluted (dollars per share/ unit) Dispositions Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Statement of Cash Flows [Abstract] 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] Depreciation and amortization of real estate assets and leasing costs Depreciation, Depletion and Amortization Depreciation of non-real estate furniture, fixtures and equipment Depreciation, Nonproduction Increase in provision for bad debts Non-cash amortization of share-based compensation awards Share-based Compensation Non-cash amortization of deferred financing costs and net debt discounts Amortization of Debt Issuance Costs and Discounts Non-cash amortization of net below market rents Amortization of above and below Market Leases Loss on early extinguishment of debt Gain (Loss) on Extinguishment of Debt (Gain) loss on sale of land Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Gains on sales of depreciable operating properties Non-cash amortization of deferred revenue related to tenant-funded tenant improvements Noncash amortization of deferred revenue related to tenant-funded tenant improvements The amortization of deferred revenue related to tenant funded tenant improvements during the period. Amortization of deferred revenue related to tenant funded tenant improvements is additional rental income over the term of the related lease and is added back to net income when calculating cash provided by (used in) operations using the indirect method. Straight-line rents Straight Line Rent Net change in other operating assets Increase (Decrease) in Operating Assets Net change in other operating liabilities Increase (Decrease) in Operating Liabilities Net cash 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] Expenditures for development properties and undeveloped land Payments to Develop Real Estate Assets Expenditures for acquisitions of development properties and undeveloped land Payments to Acquire Other Real Estate Expenditures for acquisitions of operating properties Payments to Acquire Commercial Real Estate Expenditures for operating properties and other capital assets Payments for Capital Improvements Net proceeds received from dispositions Proceeds from Sale of Real Estate Held-for-investment Decrease (increase) in acquisition-related deposits Payments for (Proceeds from) Deposits on Real Estate Acquisitions Proceeds received from repayment of note receivable Proceeds from Collection of Loans Receivable Issuance of notes receivable Payments to Acquire Loans Receivable Net cash used in 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 proceeds from issuance of common stock Redemption of Series G and H Preferred stock Payments for Repurchase of Preferred Stock and Preference Stock Net proceeds from the issuance of unsecured debt Proceeds from Issuance of Unsecured Debt Repayments of unsecured debt Repayments of Unsecured Debt Borrowings on unsecured revolving credit facility Proceeds from Long-term Lines of Credit Repayments on unsecured revolving credit facility Repayments of Long-term Lines of Credit Principal payments and repayments of secured debt Repayments of Secured Debt Proceeds from the issuance of secured debt Proceeds from Issuance of Secured Debt Financing costs Payments of Financing Costs Repurchase of common stock and restricted stock units Payments Related to Tax Withholding for Share-based Compensation Proceeds from exercise of stock options Proceeds from Stock Options Exercised Contributions from noncontrolling interests in consolidated property partnerships Proceeds from Noncontrolling Interests Distributions to noncontrolling interests in consolidated property partnerships Payments to Noncontrolling Interests Dividends and distributions paid to common stockholders and common unitholders Payments of Ordinary Dividends, Common Stock Dividends and distributions paid to preferred stockholders and preferred unitholders Dividends and distributions paid to preferred stockholders and preferred unitholders The cash outflow for the dividends and distributions to preferred shareholders and unitholders. Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Cash and cash equivalents and restricted cash, beginning of year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash and cash equivalents and restricted cash, end of year SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Uncollectible tenant receivables [Member] SEC Schedule, 12-09, Allowance, Loan and Lease Loss, Real Estate [Member] Allowance for deferred rent [Member] Allowance For Deferred Rent [Member] Allowance For Deferred Rent [Member] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Balance at Beginning of Period SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Charged to Costs and Expenses (1) SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Recoveries (Deductions) SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Balance at End of Period Notes receivable, valuation allowance Allowance for Doubtful Accounts, Premiums and Other Receivables Other Significant Noncash Transactions [Table] Other Significant Noncash Transactions [Table] Other Significant Noncash Transactions [Line Items] Other Significant Noncash Transactions [Line Items] Cash and cash equivalents Restricted cash Cash and cash equivalents and restricted cash Supplemental Cash Flow Information of the Company Cash Flow, Supplemental Disclosures [Text Block] Asset Acquisitions [Abstract] Asset Acquisitions [Abstract] Schedule of Asset Acquisitions, by Acquisition [Table] Schedule of Asset Acquisitions, by Acquisition [Table] Schedule of Asset Acquisitions, by Acquisition [Table] Kilroy Oyster Point [Member] Kilroy Oyster Point [Member] Kilroy Oyster Point [Member] Little Italy, Sand Diego, California [Member] Little Italy, Sand Diego, California [Member] Little Italy, Sand Diego, California [Member] Schedule of Asset Acquisitions, by Acquisition [Line Items] Schedule of Asset Acquisitions, by Acquisition [Line Items] [Line Items] for Schedule of Asset Acquisitions, by Acquisition [Table] Purchase price Asset Acquisition, Consideration Transferred Asset Acquisition, Consideration Transferred Asset acquisition, accrued liabilities Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Acquisition-related accrued liabilities Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Revenue And Acquisition Related Intangible Assets Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Revenue And Acquisition Related Intangible Assets Acquisition costs, capitalized Asset Acquisition, Acquisition Related Costs Capitalized Asset Acquisition, Acquisition Related Costs Capitalized Acquisition-related expenses Asset Acquisition, Acquisition Related Costs Asset Acquisition, Acquisition Related Costs Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Furniture, fixtures and other long-lived assets, net Furniture and Fixtures, Gross Notes receivable Accounts and Notes Receivable, Net Prepaid expenses & acquisition deposits Prepaid Expense Total Prepaid Expenses and Other Assets, Net Schedule of summarized quarterly financial data Quarterly Financial Information [Table Text Block] Future contractual minimum rent under operating lease Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Partially Owned Entities and Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Acquisitions Business Combinations Policy [Policy Text Block] Operating Properties and Cost Capitalization Property, Plant and Equipment, Policy [Policy Text Block] Real Estate Assets Held for Sale, Dispositions and Discontinued Operations Discontinued Operations, Policy [Policy Text Block] Revenue Recognition, Tenant Reimbursements and Other Property Income Revenue Recognition Leases, Operating [Policy Text Block] Allowances for Uncollectible Tenant and Deferred Rent Receivables Receivables, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Marketable Securities Marketable Securities, Policy [Policy Text Block] Deferred Compensation Plan Compensation Related Costs, Policy [Policy Text Block] Deferred Leasing Costs Deferred Charges, Policy [Policy Text Block] Deferred Financing Costs, and Debt Discounts and Premiums Debt, Policy [Policy Text Block] Noncontrolling Interest and Partnership Interests Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] Equity Offerings Stockholders' Equity, Policy [Policy Text Block] Share-based Incentive Compensation Accounting Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Basic and Diluted Net Income Available to Common Stockholders/ Unitholders per Share/ Unit Earnings Per Share, Policy [Policy Text Block] Fair Value Measurements Fair Value of Financial Instruments, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Uncertain Tax Positions Income Tax Uncertainties, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Segment Segment Reporting Disclosure [Text Block] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Market measure-based RSU estimate of probable [Member] Market Measure-Based RSU Estimate of Probable [Member] Market Measure-Based RSU Estimate of Probable [Member] Executive officer share-based compensation programs [Member] Executive Officer Share-Based Compensation Programs [Member] Executive Officer Share-Based Compensation Programs [Member] 2018 Performance-Based RSUs [Member] 2018 Performance-Based RSUs [Member] 2018 Performance-Based RSUs [Member] Time-Based Restricted Stock Units (RSUs), 2018 Special Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2018 Special Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2018 Special Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2018 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2018 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2018 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2017 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2017 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2017 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2016 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2016 Time-Based RSU Grant [Member] Time-Based Restricted Stock Units (RSUs), 2016 Time-Based RSU Grant [Member] 2017 Performance-Based RSUs [Member] 2017 Performance-Based RSUs [Member] 2017 Performance-Based RSUs [Member] December 2018 Time-Based RSUs [Member] [Member] December 2018 Time-Based RSU Grant [Member] [Member] December 2018 Time-Based RSU Grant [Member] [Member] Vesting criteria, one Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting, Criteria One Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting, Criteria One Vesting criteria, two Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting, Criteria Two Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting, Criteria Two Fair value RSUs granted Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Grants In Period, Grant Date Fair Value The total fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans. Fair value per share (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price RSUs granted (in units) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted Receivables Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Total Stockholders' Equity Parent [Member] Preferred Stock [Member] Preferred Stock [Member] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Distributions in Excess of Earnings [Member] Accumulated Distributions in Excess of Net Income [Member] Noncontrolling Interests [Member] Beginning Balance Beginning balance, shares outstanding (in shares) Common Stock, Shares, Outstanding Issuance of common stock Stock Issued During Period, Value, New Issues Issuance of common stock (in shares) Stock Issued During Period, Shares, New Issues Issuance of share-based compensation awards Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Exercise of stock options (in shares) Repurchase of common stock, stock options and restricted stock units Adjustments Related to Tax Withholding for Share-based Compensation Repurchase of common stock, stock options and restricted stock units (in shares) Shares Paid for Tax Withholding for Share Based Compensation Settlement of restricted stock units for shares of common stock (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Exchange of common units of the Operating Partnership Stock Issued During Period, Value, Conversion of Units Exchange of common units of the Operating Partnership (in shares) Stock Issued During Period, Shares, Conversion of Units Contributions from noncontrolling interests in consolidated property partnerships Noncontrolling Interest, Increase from Subsidiary Equity Issuance Adjustment for noncontrolling interest in the Operating Partnership Adjustments to Additional Paid in Capital, Other Dividends declared per share of common stock and common unit Dividends, Common Stock Ending Balance Ending balance, shares outstanding (in shares) Distributions declared per common unit (in dollars per units) Distributions Per Limited Partnership and General Partnership Unit, Outstanding, Basic Quarterly Financial Information of the Operating Partnership (Unaudited) Quarterly Financial Information [Text Block] Restricted cash Restricted Cash Net income available to common unitholders Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Real estate investment [Member] Real Estate Investment [Member] Class of Stock [Domain] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares outstanding Income Statement [Abstract] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Rental [Member] Rental [Member] Rental [Member] Tenant reimbursements [Member] Tenant Reimbursements [Member] Tenant Reimbursements [Member] Other property income [Member] Real Estate, Other [Member] Real estate [Member] Real Estate [Member] REVENUES: Revenues [Abstract] Revenues EXPENSES: Operating Expenses [Abstract] Property expenses Cost of Goods and Services Sold Real estate taxes Real Estate Tax Expense Ground leases Operating Leases, Rent Expense General and administrative expenses General and Administrative Expense Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Total expenses Operating Expenses OTHER (EXPENSES) INCOME: Nonoperating Income (Expense) [Abstract] Interest income and other net investment gain/loss Interest Income And Other Net Investment Gain (Loss) Income derived from investments in debt and equity securities and on cash and cash equivalents and the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading. Interest income represents earnings which reflect the time value of money or transactions in which the payments are for the use or forbearance of money. Dividend income represents a distribution of earnings to shareholders by investee companies. Interest expense Interest Expense Loss on early extinguishment of debt Gains on sales of depreciable operating properties Total other income (expenses) Nonoperating Income (Expense) NET INCOME Net income attributable to noncontrolling common units of the Operating Partnership Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable Net income attributable to noncontrolling interests in consolidated property partnerships Net Income (Loss) Attributable to Noncontrolling Interest in Consolidated Subsidiary Net Income (Loss) Attributable to Noncontrolling Interest in Consolidated Subsidiary Total income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION / KILROY REALTY, L.P. Preferred dividends Redeemable Preferred Stock Dividends Original issuance costs of redeemed preferred stock and preferred units Total preferred dividends NET INCOME AVAILABLE TO COMMON STOCKHOLDERS/UNITHOLDERS Net income available to common stockholders per share - basic (in dollars per share) Net income available to common stockholders per share - diluted (in dollars per share) Weighted average shares of common stock outstanding – basic (in shares) Weighted average shares of common stock outstanding – diluted (in shares) Prepaid expenses and other assets, net Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying value [Member] Reported Value Measurement [Member] Fair value [Member] Estimate of Fair Value Measurement [Member] Secured debt [Member] Unsecured debt [Member] Unsecured Debt [Member] Unsecured line of credit [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Fair value (Level 2) [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Debt instrument, fair value disclosure Debt Instrument, Fair Value Disclosure Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table] Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table] Parking Revenue [Member] Parking Revenue [Member] Parking Revenue [Member] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Fixed-price Contract [Member] Fixed-price Contract [Member] Ownership [Axis] Ownership [Axis] Ownership [Domain] Ownership [Domain] 100 First LLC and 303 Second LLC [Member] 101 First LLC and 303 Second LLC [Member] 101 First LLC and 303 Second LLC [Member] Kilroy Realty Finance, Inc. [Member] Kilroy Realty Finance, Inc. [Member] Kilroy Realty Finance, Inc. [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer concentration risk [Member] Customer Concentration Risk [Member] Customer concentration risk, largest tenant [Member] Customer Concentration Risk, Largest Tenant [Member] Customer Concentration Risk, Largest Tenant [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Washington [Member] WASHINGTON 100 First LLC & 303 Second LLC [Member] 100 First LLC & 303 Second LLC [Member] 100 First LLC & 303 Second LLC [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Lease Agreements [Member] Lease Agreements [Member] Properties held for sale [Member] Properties Held for Sale [Member] Properties Held for Sale [Member] Building and building improvements [Member] Building and Building Improvements [Member] Leasehold improvements [Member] Leasehold Improvements [Member] Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] Revenues Revenue from Contract with Customer, Including Assessed Tax Number of VIEs Variable Interest Entity, Unavailability of Information, Number of Entities VIE asset amount Variable Interest Entity, Consolidated, Carrying Amount, Assets VIE, carrying amount, liabilities Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Noncontrolling interest in consolidated subsidiary Depreciation of real estate SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation, Depreciation Expense Finite-lived intangible asset, useful life Finite-Lived Intangible Asset, Useful Life Number of consolidated property partnerships Number of Consolidated Property Partnerships Number of Consolidated Property Partnerships Percentage of general partnership interest owned by wholly-owned subsidiary of the Company Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest REIT annual taxable income distribution requirement percentage REIT annual taxable income distribution requirement percentage REIT annual taxable income distribution requirement percentage Company annual taxable income distribution Company annual taxable income distribution Company annual taxable income distribution Income tax provision Income Tax Expense (Benefit) Number of operating segments Number of Operating Segments Number of development projects Number of Development Projects Number of Development Projects Concentration risk, percentage Concentration Risk, Percentage Net cash provided by (used in) investing activities Acquisition-related expenses Business Combination, Acquisition Related Costs Initial premium on outstanding amount of secured debt Unamortized discount (premium), net Debt Instrument, Unamortized Discount (Premium), Net Preferred stock dividend rate (percentage) Cash, FDIC insured amount Cash, FDIC Insured Amount Number of ground leases Number of Ground Leases Number of Ground Leases Operating lease, right-of-use asset Operating Lease, Right-of-Use Asset Operating lease, liability Operating Lease, Liability Line of credit facility, maximum borrowing capacity Long-term debt Long-term Debt Secured debt Schedule operating properties and land dispositions Disposal Groups, Including Discontinued Operations [Table Text Block] SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward] SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward] Accumulated depreciation, beginning of year SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation Total additions during period SEC Schedule III, Real Estate Accumulated Depreciation, Period Increase Total increase in accumulated depreciation on real estate investments for the period. Write-offs due to sale SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation, Investment in Real Estate Sold Properties held for sale SEC Schedule III, Real Estate Accumulated Depreciation, Deductions, Assets Held for Sale Decrease in accumulated depreciation for the period attributed to assets held for sale. Other SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation, Other Deduction Total deductions during period SEC Schedule III, Real Estate Accumulated Depreciation, Period Decrease Total decrease in accumulated depreciation on real estate investments for the period. 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land parcel [Member] Washington - Land Parcel [Domain] Washington - Land Parcel [Domain] Redwood LLC [Member] Redwood LLC [Member] Redwood LLC [Member] Real Estate Properties [Line Items] Real Estate Properties [Line Items] Stabilized occupancy Lease-Up Properties, Maximum Stabilized Occupacy, Percentage Lease-Up Properties, Maximum Stabilized Occupacy, Percentage Lease-up properties, maximum stabilized occupancy, duration Lease-Up Properties, Maximum Stabilized Occupancy, Duration Lease-Up Properties, Maximum Stabilized Occupancy, Duration Property Ownership Percentage Property Ownership Percentage Property Ownership Percentage Percentage of general partnership interest owned by the company in the Operating Partnership Ownership interest of noncontrolling interest Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Percentage of limited partnership interest owned by Operating Partnership Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest Summary of minimum commitment Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Assets Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Land and improvements Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land