Consolidated Statements of Capital (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 106,704	$ 19,303	$ 209,296	$ 152,378
Noncash amortization of share-based compensation			13,621	10,345
Settlement of restricted stock units for shares of common stock			0	0
Stock Issued During Period, Value, in Connection with Early Exchange of Notes				223
Contribution by noncontrolling interest in consolidated subsidiary			474	336
Preferred distributions			(9,938)	(9,938)
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			3,850	3,011
Contribution by noncontrolling interest in consolidated subsidiary				336
Kilroy Realty, L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			2,723,936	2,516,160
Net income	106,704	19,303	209,296	152,378
Issuance of common units (Note 9)			387,509	22,136
Issuance of share-based compensation awards			1,268	1,281
Noncash amortization of share-based compensation			13,621	10,345
Exercise of stock options (Note 10)			11,292	20,537
Repurchase of common units and restricted stock units			(3,121)	(2,861)
Settlement of restricted stock units for shares of common stock			0	0
Stock Issued During Period, Value, in Connection with Early Exchange of Notes				223
Contribution by noncontrolling interest in consolidated subsidiary			474	336
Preferred distributions			(9,938)	(9,938)
Distributions declared per common unit ($0.35 per unit)			(97,275)	(90,228)
Ending Balance	3,237,062	2,620,369	3,237,062	2,620,369
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			192,411	192,411
Ending Balance	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			$ 2,521,900	$ 2,315,361
Beginning Balance units			88,063,884	83,959,144
Net income			$ 209,085	$ 152,177
Issuance of common units, units (Note 9)			5,640,033	370,700
Issuance of common units (Note 9)			$ 387,509	$ 22,136
Issuance of share-based compensation awards			1,268	1,281
Noncash amortization of share-based compensation			$ 13,621	$ 10,345
Exercise of stock options (Note 10)			265,000	482,000
Exercise of stock options (Note 10)			$ 11,292	$ 20,537
Repurchase of common units and restricted stock units, units			(39,317)	(48,017)
Repurchase of common units and restricted stock units			$ (3,121)	$ (2,861)
Settlement of restricted stock units, units			78,937	108,529
Settlement of restricted stock units for shares of common stock			$ 0	$ 0
Stock Issued During Period, Shares, in Connection with Early Exchange of Notes				431,270
Stock Issued During Period, Value, in Connection with Early Exchange of Notes				$ 223
Stock Received During Period, Call Options				(111,206)
Preferred distributions			(9,938)	$ (9,938)
Distributions declared per common unit ($0.35 per unit)			(97,275)	(90,228)
Ending Balance	$ 3,034,341	$ 2,419,033	$ 3,034,341	$ 2,419,033
Ending Balance units	94,008,537	85,192,420	94,008,537	85,192,420
Kilroy Realty, L.P. [Member] | Total Partners Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 2,714,311	$ 2,507,772
Net income			209,085	152,177
Issuance of common units (Note 9)			387,509	22,136
Issuance of share-based compensation awards			1,268	1,281
Noncash amortization of share-based compensation			13,621	10,345
Exercise of stock options (Note 10)			11,292	20,537
Repurchase of common units and restricted stock units			(3,121)	(2,861)
Settlement of restricted stock units for shares of common stock			0	0
Stock Issued During Period, Value, in Connection with Early Exchange of Notes				223
Preferred distributions			(9,938)	(9,938)
Distributions declared per common unit ($0.35 per unit)			(97,275)	(90,228)
Ending Balance	$ 3,226,752	$ 2,611,444	3,226,752	2,611,444
Kilroy Realty, L.P. [Member] | Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			9,625	8,388
Net income			211	201
Contribution by noncontrolling interest in consolidated subsidiary			474	336
Ending Balance	$ 10,310	$ 8,925	$ 10,310	$ 8,925