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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Capitalized Interest and Loan Fees [Line Items]
Interest expense	$ 17,973	$ 14,384	$ 35,325	$ 26,213
Kilroy Realty, L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	28,731	26,668	56,246	52,843
Capitalized interest and deferred financing costs	(10,758)	(12,284)	(20,921)	(26,630)
Interest expense	$ 17,973	$ 14,384	$ 35,325	$ 26,213