Partners' Capital of the Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
General Partners' Capital Account [Abstract]
Net proceeds from issuance of common stock	$ 22,136	$ 349,951
Noncontrolling Interest, Ownership Percentage by Parent	97.90%	97.80%	97.80%
Common units held by limited partners	1,804,200	1,821,503	1,805,200
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	2.10%	2.20%	2.20%
Kilroy Realty, L.P. [Member] | Capital Units [Member]
General Partners' Capital Account [Abstract]
General Partners' Capital Account, Units Outstanding	83,388,220	82,113,491	82,153,944