Secured and Unsecured Debt of the Operating Partnership - Secured Debt (Details) - Kilroy Realty, L.P. [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	[1]	$ 2,312,318
Secured Debt [Member]
Debt Instrument [Line Items]
Total debt		379,086	$ 381,918
Unamortized deferred financing costs		(1,006)	(1,083)
Total secured debt, net		378,080	380,835
Unamortized premium		$ 5,800	6,200
Secured Debt [Member] | 4.27% Mortgage Payable due Feb. 01, 2018 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate (percent)	[2],[3]	4.27%
Effective interest rate (percent)	[2],[4]	4.27%
Maturity Date	[3]	Feb. 01, 2018
Total debt	[3]	$ 127,684	128,315
Secured Debt [Member] | 4.48% Mortgage Payable due July 1, 2027 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate (percent)	[2],[3]	4.48%
Effective interest rate (percent)	[2],[3],[4]	4.48%
Maturity Date	[3]	Jul. 01, 2027
Total debt	[3]	$ 95,961	96,354
Secured Debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate (percent)	[2],[3],[5]	6.05%
Effective interest rate (percent)	[2],[3],[4],[5]	3.50%
Maturity Date	[3],[5]	Jun. 01, 2019
Total debt	[3],[5]	$ 85,037	85,890
Secured Debt [Member] | 6.51% Mortgage Payable due Feb. 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate (percent)	[2]	6.51%
Effective interest rate (percent)	[2],[4]	6.51%
Maturity Date		Feb. 01, 2017
Total debt		$ 65,281	65,563
Secured Debt [Member] | 7.15% Mortgage Payable due May 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate (percent)	[2]	7.15%
Effective interest rate (percent)	[2],[4]	7.15%
Maturity Date		May 01, 2017
Total debt		$ 3,314	3,987
Secured Debt [Member] | Other [Member]
Debt Instrument [Line Items]
Total debt		$ 1,809	$ 1,809

[1] Includes gross principal balance of outstanding debt

[2] All interest rates presented are fixed-rate interest rates.

[3] The secured debt and the related properties that secure the debt are held in a special purpose entity and the properties are not available to satisfy the debts and other obligations of the Company or the Operating Partnership.

[4] Represents the effective interest rate including the amortization of initial issuance discounts/premiums excluding the amortization of deferred financing costs.

[5] Amounts reported include the amounts of unamortized debt premiums of $5.8 million and $6.2 million as of March 31, 2016 and December 31, 2015