Secured and Unsecured Debt of the Operating Partnership (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Terms of the Credit Facility
Credit Facility	$ 0		$ 182,000
Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Credit Facility	0		182,000
Kilroy Realty, L.P. [Member] | Line of Credit [Member]
Terms of the Credit Facility
Credit Facility	0	[1]	182,000
Remaining borrowing capacity	500,000		318,000
Total borrowing capacity	$ 500,000	[2]	$ 500,000	[2]
Interest rate		[3]	2.05%	[3]
Facility fee - annual rate	0.35%	[4]	0.35%	[4]
Maturity date	August 2015	[5]	August 2015	[5]

[1] As of March 31, 2012, there were no borrowings outstanding on the Credit Facility.

[2] We may elect to borrow, subject to bank approval, up to an additional $200.0 million under an accordion feature under the terms of the Credit Facility.

[3] The Credit Facility interest rate was calculated based on an annual rate of LIBOR plus 1.750% as of both March 31, 2012 and December 31, 2011. No interest rate is shown as of March 31, 2012 because no borrowings were outstanding.

[4] The facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, we also incurred origination and legal costs of approximately $8.3 million that are currently being amortized through the maturity date of the Credit Facility.

[5] Under the terms of the Credit Facility, we may exercise an option to extend the maturity date by one year.