Quarterly Financial Information of the Company (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues	$ 111,111	[1]	$ 104,293	[1]	$ 97,111	[1]	$ 92,397	[1]	$ 94,226	[1]	$ 86,398	[1]	$ 81,002	[1]	$ 76,003	[1]	$ 404,912	$ 337,629	$ 254,994
Net Operating Income from continuing operations	79,276	[1],[2]	72,251	[1],[2]	68,437	[1],[2]	67,791	[1],[2]	67,777	[1],[2]	60,268	[1],[2]	56,910	[1],[2]	53,660	[1],[2]
Income (loss) from continuing operations	3,911	[1]	(665)	[1]	36	[1]	2,165	[1]	(16)	[1]	(3,391)	[1]	(1,071)	[1]	750	[1]	5,447	(3,728)	(427)
Income from discontinued operations	189,720	[1]	3,187	[1]	2,241	[1]	76,506	[1]	44,876	[1]	17,681	[1]	4,543	[1]	4,117	[1]	271,654	71,217	20,313
Net income	193,631		2,522		2,277		78,671		44,860		14,290		3,472		4,867		277,101	67,489	19,886
Net income attributable to Kilroy Realty Corporation	189,152		2,589		2,297		76,876		43,706		13,994		3,482		4,833		270,914	66,015	19,708
Preferred dividends and distributions	(3,313)		(5,342)		(3,097)		(9,336)		(3,799)		(3,799)		(3,799)		(3,799)		(21,088)	(15,196)	(15,196)
Net income (loss) available to common stockholders	$ 185,839	[3]	$ (2,753)	[3]	$ (800)	[3]	$ 67,540	[3]	$ 39,907	[3]	$ 10,195	[3]	$ (317)	[3]	$ 1,034	[3]	$ 249,826	$ 50,819	$ 4,512
Net income (loss) available to common stockholders per share—basic	$ 2.49	[3]	$ (0.04)	[3]	$ (0.02)	[3]	$ 1.06	[3]	$ 0.68	[3]	$ 0.17	[3]	$ (0.01)	[3]	$ 0.01	[3]	$ 3.56	$ 0.87	$ 0.07
Net income (loss) available to common stockholders per share—diluted	$ 2.45	[3]	$ (0.04)	[3]	$ (0.02)	[3]	$ 1.06	[3]	$ 0.68	[3]	$ 0.17	[3]	$ (0.01)	[3]	$ 0.01	[3]	$ 3.56	$ 0.87	$ 0.07

[1] All periods have been adjusted from amounts previously disclosed in our quarterly filings on Form 10-Q to reclassify amounts related to discontinued operations (see Note 17).

[2] Net Operating Income is defined as operating revenues (rental income, tenant reimbursements, and other property income) less property and related expenses (property expenses, real estate taxes, ground leases, and provisions for bad debts) and excludes other non−property related income and expenses such as interest income and other net investment gains (losses) and interest expense, depreciation and amortization, acquisition−related expenses and corporate general and administrative expenses.

[3] The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. The summation of the quarterly net income (loss) available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the impact of equity offerings that occurred during the years ended December 31, 2012 and 2011.