Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense	$ 70,772	$ 48,537	$ 49,721
Kilroy Realty L.P. [Member]
Debt Instrument [Line Items]
Gross interest expense	150,325	129,778	117,789
Capitalized interest and deferred financing costs	(79,553)	(81,241)	(68,068)
Interest expense	$ 70,772	$ 48,537	$ 49,721