Secured and Unsecured Debt of the Operating Partnership Capitalized Interest and Loan Fees (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Capitalized Interest and Loan Fees [Line Items]
Interest Expense	$ 16,878	$ 17,252
Kilroy Realty, L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	27,749	28,034
Capitalized interest	(10,871)	(10,782)
Interest Expense	$ 16,878	$ 17,252