Consolidated Statements of Capital (KILROY REALTY, L.P.) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 44,002	$ 101,932	$ 101,932
Noncash amortization of share-based compensation	4,302	2,233
Settlement of restricted stock units for shares of common stock	0	0
Preferred distributions	(3,313)	(3,313)
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	815		2,087
Kilroy Realty, L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2,723,936	2,516,160
Net income	44,002	101,932
Issuance of common units (Note 9)	113,097
Issuance of share-based compensation awards	413
Noncash amortization of share-based compensation	4,302	2,233
Repurchase of common units and restricted stock units	(1,821)	(1,517)
Settlement of restricted stock units for shares of common stock	0	0
Exercise of stock options (Note 10)	10,482	21
Preferred distributions	(3,313)	(3,313)
Distributions declared per common unit ($0.35 per unit)	(31,892)	(29,906)
Ending Balance	2,859,206	2,585,610
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	43,927	101,867
Issuance of common units (Note 9)	113,097
Issuance of share-based compensation awards	413
Noncash amortization of share-based compensation	4,302	2,233
Repurchase of common units and restricted stock units	(1,821)	(1,517)
Settlement of restricted stock units for shares of common stock	0	0
Exercise of stock options (Note 10)	10,482	21
Preferred distributions	(3,313)	(3,313)
Distributions declared per common unit ($0.35 per unit)	(31,892)	(29,906)
Ending Balance	2,849,506	2,577,157
Kilroy Realty, L.P. [Member] | Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	9,625	8,388
Net income	75	65
Ending Balance	9,700	8,453
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				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	43,927	101,867
Issuance of common units, units (Note 9)	1,507,393
Issuance of common units (Note 9)	113,097
Issuance of share-based compensation awards	413
Noncash amortization of share-based compensation	4,302	2,233
Repurchase of common units and restricted stock units, units	(20,429)	(26,074)
Repurchase of common units and restricted stock units	(1,821)	(1,517)
Settlement of restricted stock units, units	36,699	88,962
Settlement of restricted stock units for shares of common stock	0	0
Exercise of stock options (Note 10)	237,000	500
Exercise of stock options (Note 10)	10,482	21
Preferred distributions	(3,313)	(3,313)
Distributions declared per common unit ($0.35 per unit)	(31,892)	(29,906)
Ending Balance	$ 2,657,095	$ 2,384,746
Ending Balance units	89,824,547	84,022,532