Secured and Unsecured Debt of the Operating Partnership - Unsecured 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
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Total secured debt, net		$ 1,657,374	$ 1,656,776
Unsecured Senior Notes [Member] | 4.375% Unsecured Senior Notes due October 2025 [Member]
Debt Instrument [Line Items]
Maturity date	[2]	Oct. 01, 2025
Stated coupon rate (percent)	[2]	4.375%
Effective interest rate (percent)	[2],[3]	4.44%
Total debt	[2]	$ 400,000	400,000
Unamortized discount and deferred financing costs		(5,261)	(5,400)
Total secured debt, net		$ 394,739	394,600
Unsecured Senior Notes [Member] | 4.250% Unsecured Senior Notes due August 2029 [Member]
Debt Instrument [Line Items]
Maturity date	[4]	Aug. 15, 2029
Stated coupon rate (percent)	[4]	4.25%
Effective interest rate (percent)	[3],[4]	4.35%
Total debt	[4]	$ 400,000	400,000
Unamortized discount and deferred financing costs		(7,095)	(7,228)
Total secured debt, net		$ 392,905	392,772
Unsecured Senior Notes [Member] | 3.800% Unsecured Senior Note due January 2023 [Member]
Debt Instrument [Line Items]
Maturity date	[5]	Jan. 15, 2023
Stated coupon rate (percent)	[5]	3.80%
Effective interest rate (percent)	[3],[5]	3.804%
Total debt	[5]	$ 300,000	300,000
Unamortized discount and deferred financing costs		(1,862)	(1,931)
Total secured debt, net		$ 298,138	298,069
Unsecured Senior Notes [Member] | 4.800% Unsecured Senior Notes due July 2018 [Member]
Debt Instrument [Line Items]
Maturity date	[5],[6]	Jul. 15, 2018
Stated coupon rate (percent)	[5],[6]	4.80%
Effective interest rate (percent)	[3],[5],[6]	4.827%
Total debt	[5],[6]	$ 325,000	325,000
Unamortized discount and deferred financing costs		(1,129)	(1,251)
Total secured debt, net		$ 323,871	323,749
Unsecured Senior Notes [Member] | 6.625% Unsecured Senior Notes due June 2020 [Member]
Debt Instrument [Line Items]
Maturity date	[7]	Jun. 01, 2020
Stated coupon rate (percent)	[7]	6.625%
Effective interest rate (percent)	[3],[7]	6.743%
Total debt	[7]	$ 250,000	250,000
Unamortized discount and deferred financing costs		(2,279)	(2,414)
Total secured debt, net		$ 247,721	$ 247,586

[1] Includes gross principal balance of outstanding debt

[2] Interest on these notes is payable semi-annually in arrears on April 1st and October 1st of each year.

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

[4] Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year.

[5] Interest on these notes is payable semi-annually in arrears on January 15th and July 15th of each year.

[6] In October 2015, certain common limited partners in the Operating Partnership that previously contributed their interests in the property at 6255 W. Sunset Blvd., Los Angeles, California to the Operating Partnership entered into an agreement with the Company. Pursuant to this agreement, such common limited partners will reimburse the Company for a portion of any amounts the Company may be required to pay pursuant to its guarantee of the Operating Partnership’s 4.800% Senior Notes due 2018 or that the Company may otherwise become required to pay under applicable law with respect to such notes.

[7] Interest on these notes is payable semi-annually in arrears on June 1st and December 1st of each year.