CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 53,493	$ 42,880	$ 507,411	$ 54,071	$ 24,352	$ 45,418	$ 603,784	$ 123,841
Non-cash amortization of share-based compensation (Note 9)	11,477	11,193	9,604	7,794	13,576	8,653
Settlement of restricted stock units			0	0		0
Distributions to noncontrolling interests in consolidated property partnerships	(7,922)	(4,692)	(11,680)	(1,458)	(4,281)	(2,617)
Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	5,693,465	5,702,892	5,277,321	5,253,589	5,277,515	4,570,858	5,277,321	4,570,858
Net income	53,493	42,880	507,411	54,071	24,352	45,418	603,784	123,841
Issuance of common units				(74)	(45)	721,794
Issuance of share-based compensation awards	650	645	1,950	1,101	805	1,720
Non-cash amortization of share-based compensation (Note 9)	11,477	11,193	9,604	7,794	13,576	8,653
Repurchase of common units, stock options and restricted stock units	(282)		(21,137)	(3,353)	(735)	(9,799)
Distributions to noncontrolling interests in consolidated property partnerships	(7,922)	(4,692)	(11,680)	(1,458)	(4,281)	(2,617)
Distributions declared per common unit	(61,834)	(59,453)	(60,577)	(59,706)	(57,598)	(58,512)
Contributions from noncontrolling interests in consolidated property partnerships	1,591
Ending balance	$ 5,690,638	$ 5,693,465	$ 5,702,892	$ 5,251,964	$ 5,253,589	$ 5,277,515	$ 5,690,638	$ 5,251,964
Partners' Capital [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)	117,604,784	117,600,944	117,186,401	117,111,124	117,089,211	108,039,574	117,186,401	108,039,574
Beginning balance	$ 5,500,753	$ 5,512,175	$ 5,079,818	$ 5,049,844	$ 5,074,003	$ 4,369,758	$ 5,079,818	$ 4,369,758
Net income	47,488	36,193	502,517	49,728	19,838	$ 40,389
Issuance of common units (in units)						8,897,110
Issuance of common units				(74)	(45)	$ 721,794
Issuance of share-based compensation awards	650	645	1,950	1,101	805	1,720
Non-cash amortization of share-based compensation (Note 9)	$ 11,477	$ 11,193	$ 9,604	$ 7,794	$ 13,576	$ 8,653
Settlement of restricted stock units (in units)	11,743	3,840	769,701	126,740	33,581	269,972
Repurchase of common units, stock options and restricted stock units (in units)	(4,270)		(355,158)	(59,069)	(11,668)	(117,445)
Repurchase of common units, stock options and restricted stock units	$ (282)		$ (21,137)	$ (3,353)	$ (735)	$ (9,799)
Distributions declared per common unit	$ (61,834)	$ (59,453)	$ (60,577)	(59,706)	$ (57,598)	$ (58,512)
Contributions from noncontrolling interests in consolidated property partnerships				$ 6,034
Ending balance (in units)	117,612,257	117,604,784	117,600,944	117,178,795	117,111,124	117,089,211	117,612,257	117,178,795
Ending balance	$ 5,498,252	$ 5,500,753	$ 5,512,175	$ 5,051,368	$ 5,049,844	$ 5,074,003	$ 5,498,252	$ 5,051,368
Noncontrolling Interests [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	6,465	7,041	9,780	5,043	4,734	5,601
Distributions to noncontrolling interests in consolidated property partnerships	(7,922)	(4,692)	(11,680)	(1,458)	(4,281)	(2,617)
Noncontrolling Interests [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	192,712	190,717	197,503	203,745	203,512	201,100	197,503	201,100
Net income	6,005	6,687	4,894	4,343	4,514	5,029
Distributions to noncontrolling interests in consolidated property partnerships	(7,922)	(4,692)	(11,680)	(1,458)	(4,281)	(2,617)
Contributions from noncontrolling interests in consolidated property partnerships	1,591			(6,034)
Ending balance	$ 192,386	$ 192,712	$ 190,717	$ 200,596	$ 203,745	$ 203,512	$ 192,386	$ 200,596