CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 47,215	$ 41,794	$ 31,755	$ 40,971	$ 89,009	$ 72,726
Non-cash amortization of share-based compensation	8,732	8,817	11,503	5,094
Settlement of restricted stock units	0	0		0
Distributions to noncontrolling interests in consolidated property partnerships	(1,487)	(6,309)	(4,288)	(2,177)
Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Opening adjustment to Partners’ Capital upon adoption of ASC 842 (Note 1)							$ (3,146)
Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,021	4,891	4,206	4,725
Distributions to noncontrolling interests in consolidated property partnerships	(1,487)	(6,309)	(4,288)	(2,177)
Kilroy Realty L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	4,183,182	4,201,261	3,947,472	3,960,316	4,201,261	3,960,316
Net income	47,215	41,794	31,755	40,971	89,009	72,726
Issuance of common units			124,147
Issuance of share-based compensation awards	820	2,210	589	1,864
Non-cash amortization of share-based compensation	8,732	8,817	11,503	5,094
Exercise of stock options	64		41
Settlement of restricted stock units	0	0		0
Repurchase and cancellation of common units, stock options, and restricted stock units	(793)	(12,130)		(13,642)
Distributions to noncontrolling interests in consolidated property partnerships	(1,487)	(6,309)	(4,288)	(2,177)
Dividends declared per common unit ($0.485 and $0.455 per unit for the three months ended June 30, 2019 and 2018, and $0.455 and $0.425 per unit for the three months ended March 31, 2019, respectively)	(50,830)	(49,315)	(47,346)	(44,954)
Ending balance	$ 4,186,903	$ 4,183,182	$ 4,063,873	$ 3,947,472	$ 4,186,903	$ 4,063,873
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 1)							(3,146)
Kilroy Realty L.P. [Member] | Partners' Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in units)	102,990,311	102,772,275	100,910,398	100,697,526	102,772,275	100,697,526
Beginning balance	$ 3,987,644	$ 4,003,700	$ 3,759,196	$ 3,773,941	$ 4,003,700	$ 3,773,941
Net income	42,901	37,508	$ 28,015	36,893
Issuance of common units (in units)			1,719,195
Issuance of common units			$ 124,147
Issuance of share-based compensation awards	820	2,210	589	1,864
Non-cash amortization of share-based compensation	$ 8,732	$ 8,817	$ 11,503	$ 5,094
Exercise of stock options (in units)	1,500		1,000
Exercise of stock options	$ 64		$ 41
Settlement of restricted stock units (in units)	16,270	393,240		405,067
Repurchase and cancellation of common units, stock options, and restricted stock units (in units)	(12,759)	(175,204)		(192,195)
Repurchase and cancellation of common units, stock options, and restricted stock units	$ (793)	$ (12,130)		$ (13,642)
Dividends declared per common unit ($0.485 and $0.455 per unit for the three months ended June 30, 2019 and 2018, and $0.455 and $0.425 per unit for the three months ended March 31, 2019, respectively)	$ (50,830)	$ (49,315)	$ (47,346)	$ (44,954)
Ending balance (in units)	102,995,322	102,990,311	102,630,593	100,910,398	102,995,322	102,630,593
Ending balance	$ 3,988,538	$ 3,987,644	$ 3,876,145	$ 3,759,196	$ 3,988,538	$ 3,876,145
Kilroy Realty L.P. [Member] | 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 1)							$ (3,146)
Kilroy Realty L.P. [Member] | Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	195,538	197,561	188,276	186,375	197,561	186,375
Net income	4,314	4,286	3,740	4,078
Distributions to noncontrolling interests in consolidated property partnerships	(1,487)	(6,309)	(4,288)	(2,177)
Ending balance	$ 198,365	$ 195,538	$ 187,728	$ 188,276	$ 198,365	$ 187,728