Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Unsecured debt, net	$ 4,325,153	$ 4,020,058
Unsecured debt | Unsecured Senior Notes
Debt Instrument [Line Items]
Unamortized discount (premium), net	5,300	6,400
Unamortized debt issuance expense	15,900	19,100
Kilroy Realty L.P.
Debt Instrument [Line Items]
Long-term debt, gross	4,961,406
Unsecured debt, net	4,325,153	4,020,058
Kilroy Realty L.P. | Unsecured debt
Debt Instrument [Line Items]
Unsecured debt, net	$ 3,807,495	3,824,581
Kilroy Realty L.P. | Unsecured debt | 2.650% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	2.65%
Effective interest rate	2.654%
Long-term debt, gross	$ 450,000	450,000
Unamortized discount and deferred financing costs	(3,422)	(3,770)
Unsecured debt, net	$ 446,578	446,230
Kilroy Realty L.P. | Unsecured debt | 2.500% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	2.50%
Effective interest rate	2.56%
Long-term debt, gross	$ 425,000	425,000
Unamortized discount and deferred financing costs	(4,735)	(5,268)
Unsecured debt, net	$ 420,265	419,732
Kilroy Realty L.P. | Unsecured debt | 4.270% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.27%
Effective interest rate	4.27%
Long-term debt, gross	$ 350,000	350,000
Unamortized discount and deferred financing costs	(1,282)	(1,463)
Unsecured debt, net	$ 348,718	348,537
Kilroy Realty L.P. | Unsecured debt | 3.050% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	3.05%
Effective interest rate	3.064%
Long-term debt, gross	$ 500,000	500,000
Unamortized discount and deferred financing costs	(3,629)	(4,221)
Unsecured debt, net	$ 496,371	495,779
Kilroy Realty L.P. | Unsecured debt | 4.750% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.75%
Effective interest rate	4.80%
Long-term debt, gross	$ 400,000	400,000
Unamortized discount and deferred financing costs	(2,468)	(2,963)
Unsecured debt, net	$ 397,532	397,037
Kilroy Realty L.P. | Unsecured debt | 4.350% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.35%
Effective interest rate	4.35%
Long-term debt, gross	$ 200,000	200,000
Unamortized discount and deferred financing costs	(488)	(663)
Unsecured debt, net	$ 199,512	199,337
Kilroy Realty L.P. | Unsecured debt | 4.300% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.30%
Effective interest rate	4.30%
Long-term debt, gross	$ 50,000	50,000
Unamortized discount and deferred financing costs	(113)	(157)
Unsecured debt, net	$ 49,887	49,843
Kilroy Realty L.P. | Unsecured debt | 3.450% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	3.45%
Effective interest rate	3.47%
Long-term debt, gross	$ 403,712
Unamortized discount and deferred financing costs	(558)	(1,148)
Unsecured debt, net	$ 403,154	423,852
Kilroy Realty L.P. | Unsecured debt | 3.450% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	3.45%
Effective interest rate	3.45%
Long-term debt, gross	$ 75,000	75,000
Unamortized discount and deferred financing costs	(219)	(262)
Unsecured debt, net	$ 74,781	74,738
Kilroy Realty L.P. | Unsecured debt | 3.350% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	3.35%
Effective interest rate	3.35%
Long-term debt, gross	$ 175,000	175,000
Unamortized discount and deferred financing costs	(363)	(478)
Unsecured debt, net	$ 174,637	174,522
Kilroy Realty L.P. | Unsecured debt | 4.375% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.375%
Effective interest rate	4.444%
Long-term debt, gross	$ 400,000	400,000
Unamortized discount and deferred financing costs	(969)	(1,523)
Unsecured debt, net	$ 399,031	398,477
Kilroy Realty L.P. | Unsecured debt | 4.250% Unsecured Senior Notes
Debt Instrument [Line Items]
Stated coupon rate	4.25%
Effective interest rate	4.35%
Long-term debt, gross	$ 400,000	400,000
Unamortized discount and deferred financing costs	(2,971)	(3,503)
Unsecured debt, net	$ 397,029	$ 396,497