Consolidated Balance Sheets (KILROY REALTY, L.P.) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified			3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2013 Kilroy Realty, L.P. [Member]	Dec. 31, 2012 Kilroy Realty, L.P. [Member]	Mar. 31, 2013 Kilroy Realty, L.P. [Member] Series G Cumulative Redeemable Preferred Unit [Member]	Dec. 31, 2012 Kilroy Realty, L.P. [Member] Series G Cumulative Redeemable Preferred Unit [Member]	Mar. 31, 2013 Kilroy Realty, L.P. [Member] Series H Cumulative Redeemable Preferred Unit [Member]	Dec. 31, 2012 Kilroy Realty, L.P. [Member] Series H Cumulative Redeemable Preferred Unit [Member]	Mar. 31, 2013 Real Estate Investment [Member]	Dec. 31, 2012 Real Estate Investment [Member]	Mar. 31, 2013 Real Estate Investment [Member] Kilroy Realty, L.P. [Member]	Dec. 31, 2012 Real Estate Investment [Member] Kilroy Realty, L.P. [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets							$ 0	$ 319,770	$ 0	$ 319,770
Partners' Capital (Note 8):
General partner, units issued	75,349,705	74,926,981
General partners, units outstanding	75,349,705	74,926,981
Limited partners, units issued	1,826,503	1,826,503
Common units held by limited partners	1,826,503	1,826,503
Preferred stock dividend rate percentage			6.875%	6.875%	6.375%	6.375%
Preferred Stock Liquidation preference			$ 100,000	$ 100,000	$ 100,000	$ 100,000
Preferred Units, Issued			4,000,000	4,000,000	4,000,000	4,000,000
Preferred Units, Outstanding			4,000,000	4,000,000	4,000,000	4,000,000