Secured and Unsecured Debt of the Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended					3 Months Ended				12 Months Ended		3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Kilroy Realty, L.P. [Member]	Dec. 31, 2011 Kilroy Realty, L.P. [Member]	Mar. 31, 2012 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member]	Mar. 31, 2011 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member]	Mar. 31, 2012 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member] 3.25% Exchangeable Notes [Member]		Dec. 31, 2011 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member] 3.25% Exchangeable Notes [Member]		Mar. 31, 2012 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member] 4.25% Exchangeable Notes [Member]		Dec. 31, 2011 Kilroy Realty, L.P. [Member] Exchangeable Notes [Member] 4.25% Exchangeable Notes [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Principal amount								$ 148,000		$ 148,000		$ 172,500		$ 172,500
Unamortized discount								(132)		(924)		(11,679)		(12,684)
Net carrying amount of liability component	308,689		306,892	308,689	306,892			147,868		147,076		160,821		159,816
Carrying amount of equity component								33,675		33,675		19,835		19,835
Maturity Date								Apr. 15, 2012		Apr. 15, 2012		Nov. 15, 2014		Nov. 15, 2014
Stated coupon rate								3.25%	[1]	3.25%	[1]	4.25%	[2]	4.25%	[2]
Effective interest rate								5.45%	[3]	5.45%	[3]	7.13%	[3]	7.13%	[3]
Exchange rate per $1,000 principal value of the Exchangeable Notes, as adjusted								11.3636	[4]	11.3636	[4]	27.8307	[4]	27.8307	[4]
Exchange price, as adjusted								$ 88	[4]	$ 88	[4]	$ 35.93	[4]	$ 35.93	[4]
Number of Shares on which aggregate consideration to be delivered upon conversion is determined								1,681,813	[4]	1,681,813	[4]	4,800,796	[4]	4,800,796	[4]
Capped call transactions
Referenced shares of common stock								1,121,201	[5]	1,121,201	[5]	4,800,796	[6]	4,800,796	[6]
Exchange price including effect of capped calls								$ 102.72	[5]	$ 102.72	[5]	$ 42.81	[6]	$ 42.81	[6]
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange Abstract
Average trading price of the Companys stock	$ 42.86	$ 37.96
Interest Expense for the Exchangeable Notes
Contractual interest payments						3,035	3,035
Amortization of discount						1,797	1,688
Interest expense attributable to the Exchangeable Notes						$ 4,832	$ 4,723

[1] Interest on the 3.25% Exchangeable Notes is payable semi-annually in arrears on April 15th and October 15th of each year.

[2] Interest on the 4.25% Exchangeable Notes is payable semi-annually in arrears on May 15th and November 15th of each year.

[3] The rate at which we record interest expense for financial reporting purposes, which reflects the amortization of the discounts on the Exchangeable Notes. This rate represents our conventional debt borrowing rate at the date of issuance.

[4] The exchange rate, exchange price, and the number of shares to be delivered upon conversion are subject to adjustment under certain circumstances including increases in our common dividends.

[5] The capped calls mitigate the dilutive impact to us of the potential exchange of two-thirds of the 3.25% Exchangeable Notes into shares of common stock.

[6] The capped calls mitigate the dilutive impact to us of the potential exchange of all of the 4.25% Exchangeable Notes into shares of common stock.