Consolidated Statements of Capital (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 35,418	$ 178,113	$ 29,308	$ 44,002	$ 303,798	$ 238,604	$ 183,808
Non-cash amortization of share-based compensation					26,624	18,869	14,471
Settlement of restricted stock units for shares of common stock					0	(1)	(1)
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					(453,449)
Common shares issued in connection with settlement of 4.25% Exchangeable Senior Notes							223
Common shares received in connection with capped call option transactions							0
Contribution by noncontrolling interest in consolidated subsidiary						474	977
Distributions to noncontrolling interests in consolidated property partnerships					3,615
Preferred dividends and distributions					(13,250)	(13,250)	(13,250)
Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income					10,010	4,523	3,589
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					(124,452)
Contribution by noncontrolling interest in consolidated subsidiary						474	977
Distributions to noncontrolling interests in consolidated property partnerships					3,615
Kilroy Realty, L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		3,234,586		2,723,936	3,234,586	2,723,936	2,516,160
Net income	35,418	178,113	29,308	44,002	303,798	238,604	183,808
Issuance of common units					31,117	387,398	123,860
Issuance of common units in connection with acquisition					48,033
Issuance of share-based compensation awards					1,827	1,692	1,692
Non-cash amortization of share-based compensation					26,624	18,869	14,471
Exercise of stock options					12,208	14,573	21,092
Repurchase of common units and restricted stock units					8,875	7,081	3,533
Settlement of restricted stock units for shares of partner's capital					0	(1)	(1)
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					(453,449)
Common shares issued in connection with settlement of 4.25% Exchangeable Senior Notes							223
Common shares received in connection with capped call option transactions							0
Contribution by noncontrolling interest in consolidated subsidiary						474	977
Distributions to noncontrolling interests in consolidated property partnerships					(3,615)
Preferred dividends and distributions					(13,250)	(13,250)	(13,250)
Distributions declared per common unit					(326,585)	(130,628)	(121,563)
Ending balance	3,759,317		3,234,586		3,759,317	3,234,586	$ 2,723,936
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units, units							1,950,599
Kilroy Realty, L.P. [Member] | Total Partners Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		3,224,020		2,714,311	3,224,020	2,714,311	$ 2,507,772
Net income					300,063	238,137	183,548
Issuance of common units					31,117	387,398	123,860
Issuance of common units in connection with acquisition					48,033
Issuance of share-based compensation awards					1,827	1,692	1,692
Non-cash amortization of share-based compensation					26,624	18,869	14,471
Exercise of stock options						14,573	21,092
Repurchase of common units and restricted stock units					8,875	7,081	3,533
Settlement of restricted stock units for shares of partner's capital					0	(1)	(1)
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					(328,997)
Common shares issued in connection with settlement of 4.25% Exchangeable Senior Notes							223
Common shares received in connection with capped call option transactions							0
Preferred dividends and distributions					(13,250)	(13,250)	(13,250)
Distributions declared per common unit					(326,585)	(130,628)	(121,563)
Ending balance	3,624,179		3,224,020		3,624,179	3,224,020	2,714,311
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		192,411		192,411	192,411	192,411	192,411
Ending balance	192,411		192,411		192,411	192,411	192,411
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 3,031,609		$ 2,521,900	$ 3,031,609	$ 2,521,900	$ 2,315,361
Beginning balance units		94,023,465		88,063,884	94,023,465	88,063,884	83,959,144
Net income					$ 300,063	$ 238,137	$ 183,548
Issuance of common units					$ 31,117	$ 387,398	123,860
Issuance of common units, units					451,398	5,640,033
Issuance of common units in connection with acquisition					$ 48,033
Issuance of common units in connection with acquisition, units					867,701
Issuance of share-based compensation awards					$ 1,827	$ 1,692	1,692
Non-cash amortization of share-based compensation					26,624	18,869	14,471
Exercise of stock options					$ 12,208	$ 14,573	$ 21,092
Exercise of stock options, units					286,500	342,000	495,000
Repurchase of common units and restricted stock units					$ 8,875	$ 7,081	$ 3,533
Repurchase of common units and restricted stock units, units					137,126	101,389	58,045
Settlement of restricted stock units for shares of common stock					$ 0	$ (1)	$ (1)
Settlement of restricted stock units for shares of common stock units					109,044	78,937	141,205
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					$ (328,997)
Common shares issued in connection with settlement of 4.25% Exchangeable Senior Notes							$ 223
Common shares issued in connection with settlement of 4.25% Exchangeable Senior Notes, units							2,091,323
Common shares received in connection with capped call option transactions, units							(515,342)
Preferred dividends and distributions					(13,250)	$ (13,250)	$ (13,250)
Distributions declared per common unit					326,585	130,628	121,563
Ending balance	$ 3,431,768		$ 3,031,609		$ 3,431,768	$ 3,031,609	$ 2,521,900
Ending balance units	95,600,982		94,023,465		95,600,982	94,023,465	88,063,884
Kilroy Realty, L.P. [Member] | Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 10,566		$ 9,625	$ 10,566	$ 9,625	$ 8,388
Net income					3,735	467	260
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs					124,452
Contribution by noncontrolling interest in consolidated subsidiary						474	977
Distributions to noncontrolling interests in consolidated property partnerships					3,615
Ending balance	$ 135,138		$ 10,566		$ 135,138	$ 10,566	$ 9,625