Secured and Unsecured Debt of the Operating Partnership (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Capitalized interest and loan fees
Interest expense	$ 21,163		$ 20,876
Kilroy Realty, L.P. [Member]
Capitalized interest and loan fees
Gross interest expense	24,994		22,855
Capitalized interest	(3,831)		(1,979)
Interest expense	21,163		20,876
Debt [Member] | Kilroy Realty, L.P. [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Remaining 2012	251,758	[1]
2013	6,373
2014	262,443
2015	357,382
2016	156,551
Thereafter	768,476
Total	$ 1,802,983	[2]

[1] Includes the 3.25% Exchangeable Notes with an aggregate principal amount of $148.0 million that we repaid in April 2012 upon maturity (see Note 17).

[2] Includes gross principal balance of outstanding debt before impact of all debt discounts and premiums.