CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 77,922	$ 41,794	$ 166,890	$ 40,971	$ 215,229	$ 277,926	$ 180,615
Redemption of Series G & H Preferred stock							(200,000)
Non-cash amortization of share-based compensation					32,813	35,890	26,319
Settlement of restricted stock units					0	0	0
Distributions to noncontrolling interests in consolidated property partnerships					(12,952)	(11,803)	(16,542)
Preferred dividends and distributions							(5,774)
Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Opening adjustment to Partners’ Capital upon adoption of ASC 842 (Note 2)								$ (3,146)
Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income					19,786	19,511	16,003
Distributions to noncontrolling interests in consolidated property partnerships					(12,952)	(11,803)	(16,542)
Kilroy Realty L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		4,201,261		3,960,316	4,201,261	3,960,316	3,759,317
Net income	77,922	41,794	166,890	40,971	215,229	277,926	180,615
Redemption of Series G & H Preferred stock							(200,000)
Issuance of common units					353,722	130,693	326,058
Issuance of share-based compensation awards					4,664	3,926	5,890
Non-cash amortization of share-based compensation					32,813	35,890	26,319
Exercise of stock options					703	41	12,179
Settlement of restricted stock units					0	0	0
Repurchase of common units and restricted stock units					(14,861)	(16,553)	(12,986)
Contributions from noncontrolling interest in consolidated property partnership						8,273	54,604
Distributions to noncontrolling interests in consolidated property partnerships					(12,952)	(11,803)	(16,542)
Preferred dividends and distributions							(5,774)
Distributions declared per common unit					(206,575)	(187,448)	(169,364)
Ending balance	4,570,858		4,201,261		4,570,858	4,201,261	3,960,316
Kilroy Realty L.P. [Member] | Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Opening adjustment to Partners’ Capital upon adoption of ASC 842 (Note 2)								(3,146)
Kilroy Realty L.P. [Member] | Total Partners Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		4,003,700		3,773,941	4,003,700	3,773,941	3,624,179
Net income					198,738	263,210	167,440
Redemption of Series G & H Preferred stock							(200,000)
Issuance of common units					353,722	130,693	326,058
Issuance of share-based compensation awards					4,664	3,926	5,890
Non-cash amortization of share-based compensation					32,813	35,890	26,319
Exercise of stock options					703	41	12,179
Repurchase of common units and restricted stock units					(14,861)	(16,553)	(12,986)
Preferred dividends and distributions							(5,774)
Distributions declared per common unit					(206,575)	(187,448)	(169,364)
Ending balance	4,369,758		4,003,700		4,369,758	4,003,700	3,773,941
Kilroy Realty L.P. [Member] | Total Partners Capital [Member] | Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Opening adjustment to Partners’ Capital upon adoption of ASC 842 (Note 2)								(3,146)
Kilroy Realty L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		0		0	0	0	192,411
Redemption of Series G & H Preferred stock							(192,411)
Ending balance	0		0		0	0	0
Kilroy Realty L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 4,003,700		$ 3,773,941	$ 4,003,700	$ 3,773,941	$ 3,431,768
Beginning balance (in units)		102,772,275		100,697,526	102,772,275	100,697,526	95,600,982
Net income					$ 198,738	$ 263,210	$ 167,440
Redemption of Series G & H Preferred stock							(7,589)
Issuance of common units					$ 353,722	$ 130,693	$ 326,058
Issuance of common units (in units)					5,000,000	1,817,195	4,662,577
Issuance of share-based compensation awards					$ 4,664	$ 3,926	$ 5,890
Non-cash amortization of share-based compensation					32,813	35,890	26,319
Exercise of stock options					$ 703	$ 41	$ 12,179
Exercise of stock options (in units)					16,500	1,000	285,000
Settlement of restricted stock units (in units)					463,276	488,354	317,848
Repurchase of common units and restricted stock units					$ (14,861)	$ (16,553)	$ (12,986)
Repurchase of common units and restricted stock units (in units)					(212,477)	(231,800)	(168,881)
Preferred dividends and distributions							$ (5,774)
Distributions declared per common unit					$ (206,575)	$ (187,448)	(169,364)
Ending balance	$ 4,369,758		$ 4,003,700		$ 4,369,758	$ 4,003,700	$ 3,773,941
Ending balance (in units)	108,039,574		102,772,275		108,039,574	102,772,275	100,697,526
Kilroy Realty L.P. [Member] | Partners Capital Common Unit [Member] | Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Opening adjustment to Partners’ Capital upon adoption of ASC 842 (Note 2)								$ (3,146)
Kilroy Realty L.P. [Member] | Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 197,561		$ 186,375	$ 197,561	$ 186,375	$ 135,138
Net income					16,491	14,716	13,175
Contributions from noncontrolling interest in consolidated property partnership						8,273	54,604
Distributions to noncontrolling interests in consolidated property partnerships					(12,952)	(11,803)	(16,542)
Ending balance	$ 201,100		$ 197,561		$ 201,100	$ 197,561	$ 186,375