Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Total Stockholders' Equity	Preferred Stock [Member]	Common Stock [Member]	Common Stock Additional Paid-in Capital	Common Stock Distributions in Excess of Earnings	Noncontrolling Interest [Member]	Kilroy Realty, L.P. [Member]
Beginning Balance at Dec. 31, 2012	$ 2,235,933	$ 2,189,630	$ 192,411	$ 749	$ 2,126,005	$ (129,535)	$ 46,303
Beginning Balance, shares at Dec. 31, 2012				74,926,981
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,388	2,410				2,410	(22)	2,388
Issuance of common stock, shares				453,679
Issuance of common stock	23,395	23,395		4	23,391
Issuance of share-based compensation awards, shares				0
Issuance of share-based compensation awards	336	336			336
Noncash amortization of share-based compensation	2,422	2,422			2,422			2,422
Repurchase of common stock and restricted stock units, shares				(33,534)
Repurchase of common stock and restricted stock units	(1,199)	(1,199)			(1,199)
Settlement of restricted stock units for shares of common stock, shares				2,579
Settlement of restricted stock units for shares of common stock					(10)
Settlement of restricted stock units for common stock value	(10)	(10)						(10)
Dividends, Preferred Stock						3,313		(3,313)
Adjustment for noncontrolling interest	0	(1,893)			(1,893)		1,893
Preferred dividends	(3,313)	(3,313)						(3,313)
Dividends declared per common share and common unit ($0.35 per share/unit)	(27,412)	(26,773)				(26,773)	(639)
Ending Balance at Mar. 31, 2013	2,232,540	2,185,005	192,411	753	2,149,052	(157,211)	47,535
Ending Balance, shares at Mar. 31, 2013				75,349,705
Beginning Balance at Dec. 31, 2013	2,516,160	2,461,312	192,411	822	2,478,975	(210,896)	54,848
Beginning Balance, shares at Dec. 31, 2013				82,153,944
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	101,932	99,845				99,845	2,087	101,932
Noncash amortization of share-based compensation	2,233	2,233			2,233			2,233
Repurchase of common stock and restricted stock units, shares				(26,074)
Repurchase of common stock and restricted stock units	(1,517)	(1,517)			(1,517)
Settlement of restricted stock units for shares of common stock, shares				88,962
Settlement of restricted stock units for shares of common stock					0
Settlement of restricted stock units for common stock value	0	0						0
Exercise of stock options, net, units				1,000
Exercise of stock options, net	21	21			21
Exchange of common units of the Operating Parternship, shares				500
Exchange of common units of the Operating Partnership		28			28		(28)
Dividends, Preferred Stock						3,313		(3,313)
Preferred dividends	(3,313)	(3,313)						(3,313)
Dividends declared per common share and common unit ($0.35 per share/unit)	(29,906)	(29,272)				(29,272)	(634)
Ending Balance at Mar. 31, 2014	$ 2,585,610	$ 2,529,337	$ 192,411	$ 822	$ 2,479,740	$ (143,636)	$ 56,273
Ending Balance, shares at Mar. 31, 2014				82,218,332