CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201602Member
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 24,352	$ 45,418	$ 47,215	$ 41,794	$ 69,770	$ 89,009
Non-cash amortization of share-based compensation (Note 7)	13,576	8,653	8,732	8,817
Settlement of restricted stock units	0	0	0	0
Exchange of common units of the Operating Partnership	0	0		0
Distributions to noncontrolling interests in consolidated property partnerships	(4,281)	(2,617)	(1,487)	(6,309)
Dividends, Common Stock	$ 57,598	$ 58,512	$ 50,830	$ 49,315
Common Stock [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Exercise of stock options (in shares)			1,500
Settlement of restricted stock units (in units)	33,581	269,972	16,270	393,240
Settlement of restricted stock units	$ 0	$ 3		$ 4
Exchange of common units of the Operating Partnership	1
Noncontrolling Interests [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	4,734	5,601	$ 5,021	4,891
Exchange of common units of the Operating Partnership	(3,762)	(81)		(78)
Distributions to noncontrolling interests in consolidated property partnerships	(4,281)	(2,617)	(1,487)	(6,309)
Dividends, Common Stock	939	$ 980	981	921
Kilroy Realty L.P. [Member]
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201602member
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	5,277,515	$ 4,570,858	4,183,182	4,201,261	4,570,858	4,201,261
Net income	24,352	45,418	47,215	41,794	69,770	89,009
Issuance of common units (Note 4)	(45)	721,794
Issuance of share-based compensation awards	805	1,720	820	2,210
Non-cash amortization of share-based compensation (Note 7)	13,576	8,653	8,732	8,817
Exercise of stock options			64
Settlement of restricted stock units	0	0	0	0
Repurchase of common units, stock options and restricted stock units	(735)	(9,799)	(793)	(12,130)
Distributions to noncontrolling interests in consolidated property partnerships	(4,281)	(2,617)	(1,487)	(6,309)
Dividends declared per common unit	(57,598)	(58,512)	(50,830)	(49,315)
Ending balance	$ 5,253,589	$ 5,277,515	$ 4,186,903	$ 4,183,182	$ 5,253,589	$ 4,186,903
Kilroy Realty L.P. [Member] | Partners' Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)	117,089,211	108,039,574	102,990,311	102,772,275	108,039,574	102,772,275
Beginning balance	$ 5,074,003	$ 4,369,758	$ 3,987,644	$ 4,003,700	$ 4,369,758	$ 4,003,700
Net income	$ 19,838	$ 40,389	42,901	37,508
Issuance of common units (in units)	0	8,897,110
Issuance of common units (Note 4)	$ (45)	$ 721,794
Issuance of share-based compensation awards	805	1,720	820	2,210
Non-cash amortization of share-based compensation (Note 7)	$ 13,576	$ 8,653	$ 8,732	$ 8,817
Exercise of stock options (in shares)			1,500
Exercise of stock options			$ 64
Settlement of restricted stock units (in units)	33,581	269,972	16,270	393,240
Repurchase of common units, stock options and restricted stock units (in units)	(11,668)	(117,445)	(12,759)	(175,204)
Repurchase of common units, stock options and restricted stock units	$ (735)	$ (9,799)	$ (793)	$ (12,130)
Dividends declared per common unit	$ (57,598)	$ (58,512)	$ (50,830)	$ (49,315)
Ending balance (in units)	117,111,124	117,089,211	102,995,322	102,990,311	117,111,124	102,995,322
Ending balance	$ 5,049,844	$ 5,074,003	$ 3,988,538	$ 3,987,644	$ 5,049,844	$ 3,988,538
Kilroy Realty L.P. [Member] | Noncontrolling Interests [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	203,512	201,100	195,538	197,561	201,100	197,561
Net income	4,514	5,029	4,314	4,286
Distributions to noncontrolling interests in consolidated property partnerships	(4,281)	(2,617)	(1,487)	(6,309)
Ending balance	$ 203,745	$ 203,512	$ 198,365	195,538	$ 203,745	198,365
Cumulative Effect, Period of Adoption, Adjustment [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance				(3,146)		(3,146)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Kilroy Realty L.P. [Member] | Partners' Capital [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance				$ (3,146)		$ (3,146)