Secured and Unsecured Debt of the Operating Partnership - Secured Debt and Additional Information (Details)	1 Months Ended	12 Months Ended
	Oct. 31, 2022 USD ($) extension_option	Dec. 31, 2023 USD ($) extension_option	Dec. 31, 2022 USD ($) extension_option	Dec. 31, 2021 USD ($)	Jul. 31, 2023 USD ($) ft² apartment_unit office_building	Mar. 31, 2023 USD ($)	Jan. 31, 2023 USD ($)
Debt Instrument [Line Items]
Net proceeds from the issuance of unsecured debt (Note 10)		$ 0	$ 0	$ 449,807,000
Secured Debt
Secured debt		603,225,000	242,938,000
Term Loan
Debt Instrument [Line Items]
Line of credit facility, accordion feature, higher borrowing capacity option							$ 100,000,000
Line of credit facility, maximum borrowing capacity							$ 650,000,000
Line of credit facility, additional borrowing capacity						$ 20,000,000
Unsecured debt
Secured Debt
Total secured debt, net		4,300,000,000	4,000,000,000
Unsecured debt | Unsecured Term Loan Facility
Debt Instrument [Line Items]
Principal amount of debt	$ 400,000,000
Net proceeds from the issuance of unsecured debt (Note 10)	$ 200,000,000
Number of extension options | extension_option	2
Extension period (in months)	12 months
Kilroy Realty L.P.
Debt Instrument [Line Items]
Number of buildings | office_building					2
Number of apartment units | apartment_unit					608
Area of Retail (in square feet) | ft²					95,000
Net proceeds from the issuance of unsecured debt (Note 10)		0	0	$ 449,807,000
Secured Debt
Long-term debt, gross		4,961,406,000
Secured debt		603,225,000	242,938,000
Kilroy Realty L.P. | 3.57% Mortgage Payable due December 2026
Secured Debt
Long-term debt, gross		156,400,000
Kilroy Realty L.P. | 5.90% Mortgage Payable due August 2034
Secured Debt
Long-term debt, gross		375,000,000
Kilroy Realty L.P. | Secured debt
Secured Debt
Secured debt		612,694,000	243,469,000
Unamortized deferred financing costs		(9,469,000)	(531,000)
Total secured debt, net		603,225,000	242,938,000
Net book value of properties pledged as collateral for secured debt		$ 817,300,000
Kilroy Realty L.P. | Secured debt | 3.57% Mortgage Payable due December 2026
Secured Debt
Stated interest rate		3.57%
Effective interest rate		3.57%
Long-term debt, gross		$ 156,386,000	159,973,000
Kilroy Realty L.P. | Secured debt | 4.48% Mortgage Payable due July 2027
Secured Debt
Stated interest rate		4.48%
Effective interest rate		4.48%
Long-term debt, gross		$ 81,308,000	83,496,000
Kilroy Realty L.P. | Secured debt | 5.90% Mortgage Payable due August 2034
Debt Instrument [Line Items]
Principal amount of debt					$ 375,000,000
Secured Debt
Stated interest rate		5.90%			5.90%
Effective interest rate		5.90%
Long-term debt, gross		$ 375,000,000	$ 0
Kilroy Realty L.P. | Unsecured debt | Unsecured Term Loan Facility
Debt Instrument [Line Items]
Principal amount of debt						$ 520,000,000
Number of extension options | extension_option		2	2
Extension period (in months)		12 months	12 months
Secured Debt
Total secured debt, net		$ 520,000,000
Kilroy Realty L.P. | Unsecured debt | Unsecured Term Loan Facility | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on SOFR and LIBOR	0.95%
Kilroy Realty L.P. | Line of credit | Unsecured Term Loan Facility
Debt Instrument [Line Items]
Contingent additional borrowings	$ 100,000,000	130,000,000	$ 100,000,000
Line of credit facility, maximum borrowing capacity		520,000,000	400,000,000
Secured Debt
Unamortized deferred financing costs		$ (2,300,000)	$ (4,500,000)
Kilroy Realty L.P. | Line of credit | Unsecured Term Loan Facility | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on SOFR and LIBOR		0.95%	0.95%