Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Capitalized Interest and Loan Fees [Line Items]
Interest expense	$ 15,884	$ 11,727	$ 30,328	$ 22,970
Kilroy Realty L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	36,400	32,607	72,262	63,287
Capitalized interest and deferred financing costs	(20,516)	(20,880)	(41,934)	(40,317)
Interest expense	$ 15,884	$ 11,727	$ 30,328	$ 22,970