Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Interest expense	$ 55,803	$ 57,682	$ 67,571
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Gross interest expense	105,263	109,647	114,661
Capitalized interest	49,460	51,965	47,090
Interest expense	$ 55,803	$ 57,682	$ 67,571