Basis of Presentation and Significant Accounting Policies (Details)	1 Months Ended		12 Months Ended
	Aug. 31, 2012	Mar. 31, 2012	Dec. 31, 2016 USD ($) property shares	Dec. 31, 2015 USD ($) property shares	Dec. 31, 2014 USD ($)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Restricted Cash			$ 48,400,000
VIE Asset Amount			654,300,000	$ 203,300,000
VIE, carrying amount, liabilities			166,100,000	28,800,000
Noncontrolling interest in consolidated subsidiary			130,732,000	6,520,000
Depreciation of real estate			171,983,000	159,524,000	$ 153,841,000
Amortization of debt issuance costs			1,400,000
Initial premium on outstanding amount of secured debt			$ 4,400,000
REIT annual taxable income distribution requirement percentage			90.00%
Company annual taxable income distribution			100.00%
Concentration risk, percentage			37.30%
Cash, FDIC insured amount			$ 250,000
Accounting Standards Update 2015-03 and 2015-15 [Member] | Secured debt, net [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt issuance costs, net				1,100,000
Accounting Standards Update 2015-03 and 2015-15 [Member] | Unsecured debt, net [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt issuance costs, net				12,000,000
Accounting Standards Update 2015-03 and 2015-15 [Member] | Prepaid expenses and other current assets [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Debt issuance costs, line of credit arrangements, net				4,600,000
Real estate investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE Asset Amount			588,600,000	187,300,000
Undeveloped land [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Business acquisition, acquisition related costs capitalized			$ 500,000	$ 1,100,000	$ 4,500,000
Properties held for sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property			1
Torrey Santa Fe Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property			4
Torrey Santa Fe Properties [Member] | Properties held for sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property				4
Minimum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives			25 years
Minimum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives			1 year
Maximum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives			40 years
Maximum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives			20 years
Lease Agreements [Member] | Minimum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life			1 year
Lease Agreements [Member] | Maximum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life			20 years
Kilroy Realty Finance, Inc. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of general partnership interest owned by wholly-owned subsidiary of the Company			1.00%
Secured debt [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amortization of debt issuance costs				$ 1,100,000
Unamortized discount (premium), Net				(6,200,000)
Secured debt [Member] | Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Initial premium on outstanding amount of secured debt			$ 4,400,000
Unsecured debt [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amortization of debt issuance costs			10,100,000	12,000,000
Unamortized discount (premium), Net			(6,600,000)	7,400,000
Line of credit [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Amortization of debt issuance costs			$ 5,700,000	$ 4,300,000
Series G Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares			4,000,000	4,000,000
Preferred stock dividend rate (percentage)			6.875%	6.875%
Series H Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares			4,000,000	4,000,000
Preferred stock dividend rate (percentage)			6.375%	6.375%
Series G Preferred Stock [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares				4,000,000
Preferred stock dividend rate (percentage)		6.875%	6.875%	6.875%
Series G Preferred Stock [Member] | Series G Cumulative Redeemable Preferred Unit [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares			4,000,000
Series H Preferred Stock [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares				4,000,000
Preferred stock dividend rate (percentage)	6.375%		6.375%	6.375%
Series H Preferred Stock [Member] | Series H Cumulative Redeemable Preferred Unit [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares			4,000,000
Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property			12