Secured and Unsecured Debt of the Operating Partnership - Debt Maturities (Details) - Kilroy Realty L.P. [Member] - USD ($)	Oct. 25, 2021	Oct. 07, 2021	Sep. 30, 2021
Stated debt maturities and scheduled amortization payments
Remaining 2021			$ 1,356,000
2022			5,554,000
2023			305,775,000
2024			431,006,000
2025			406,246,000
2026			401,316,000
Thereafter			2,399,125,000
Total debt			3,950,378,000
Unsecured term loan facility, unsecured senior notes and secured debt [Member]
Stated debt maturities and scheduled amortization payments
Unamortized deferred financing costs			20,000,000
Unsecured senior notes [Member]
Stated debt maturities and scheduled amortization payments
Unamortized discount			$ 7,500,000
Unsecured senior notes [Member] | Unsecured Senior Notes - Registered Offering [Member] | Subsequent event [Member]
Stated debt maturities and scheduled amortization payments
Principal amount of debt		$ 450,000,000
Term of loan		12 years
Stated interest rate on debt (percent)		2.65%
Unsecured senior notes [Member] | 3.800% Unsecured Senior Notes due January 2023 [Member] | Subsequent event [Member]
Stated debt maturities and scheduled amortization payments
Stated interest rate on debt (percent)	3.80%
Repayment of debt	$ 300,000,000