Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) (USD $) In Thousands, except 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
Numerator:
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 (Loss) from Continuing Operations Attributable to Noncontrolling Interest																	(383)	(545)	(468)
PREFERRED DISTRIBUTIONS	(3,313)		(5,342)		(3,097)		(9,336)		(3,799)		(3,799)		(3,799)		(3,799)		(21,088)	(15,196)	(15,196)
Allocation to participating securities (nonvested units and RSUs)																	(1,602)	(1,309)	(1,151)
Numerator for basic and diluted (loss) income from continuing operations available to common unitholders																	(16,860)	(19,688)	(16,306)
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
Income from discontinued operations attributable to noncontrolling interests in consolidated subsidiaries																	(6,570)	(2,019)	(646)
Numerator for basic and diluted net income (loss) available to common unitholders																	248,224	49,510	3,361
Denominator:
Basic weighted average vested units outstanding																	69,639,623	56,717,121	49,497,487
Effect of dilutive securities - contingently issuable shares and stock options																	0	0	0
Diluted weighted average vested units and common unit equivalents outstanding																	69,639,623	56,717,121	49,497,487
Basic earnings per unit:
Loss from continuing operations available to common stockholders per common share-basic (Note 19)																	$ (0.24)	$ (0.35)	$ (0.33)
Income from discontinued operations per common unit																	$ 3.80	$ 1.22	$ 0.40
Net income available to common unitholders per unit-basic (Note 20)	$ 2.49	[2]	$ (0.04)	[2]	$ (0.02)	[2]	$ 1.06	[2]	$ 0.68	[2]	$ 0.17	[2]	$ (0.01)	[2]	$ 0.01	[2]	$ 3.56	$ 0.87	$ 0.07
Diluted earnings per unit:
Loss from continuing operations available to common stockholders per common share-diluted (Note 19)																	$ (0.24)	$ (0.35)	$ (0.33)
Income from discontinued operations per common unit																	$ 3.80	$ 1.22	$ 0.40
Net income available to common unitholders per unit-diluted (Note 20)	$ 2.45	[2]	$ (0.04)	[2]	$ (0.02)	[2]	$ 1.06	[2]	$ 0.68	[2]	$ 0.17	[2]	$ (0.01)	[2]	$ 0.01	[2]	$ 3.56	$ 0.87	$ 0.07
Number of options, outstanding	1,540,000								5,000								1,540,000	5,000
Kilroy Realty, L.P. [Member]
Numerator:
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 (Loss) from Continuing Operations Attributable to Noncontrolling Interest																	(174)	529	162
PREFERRED DISTRIBUTIONS	(3,313)		(5,342)		(3,097)		(9,336)		(3,799)		(3,799)		(3,799)		(3,799)		(21,088)	(15,196)	(15,196)
Allocation to participating securities (nonvested units and RSUs)																	(1,602)	(1,309)	(1,151)
Numerator for basic and diluted (loss) income from continuing operations available to common unitholders																	(17,417)	(20,762)	(16,936)
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
Income from discontinued operations attributable to noncontrolling interests in consolidated subsidiaries																	(464)	0	0
Numerator for basic and diluted net income (loss) available to common unitholders																	$ 253,773	$ 50,455	$ 3,377
Denominator:
Basic weighted average vested units outstanding																	71,403,258	58,437,444	51,220,618
Effect of dilutive securities - contingently issuable shares and stock options																	0	0	0
Diluted weighted average vested units and common unit equivalents outstanding																	71,403,258	58,437,444	51,220,618
Basic earnings per unit:
Loss from continuing operations available to common stockholders per common share-basic (Note 19)																	$ (0.24)	$ (0.36)	$ (0.33)
Income from discontinued operations per common unit																	$ 3.80	$ 1.22	$ 0.40
Net income available to common unitholders per unit-basic (Note 20)	$ 2.48	[3]	$ (0.04)	[3]	$ (0.02)	[3]	$ 1.05	[3]	$ 0.68	[3]	$ 0.17	[3]	$ (0.01)	[3]	$ 0.01	[3]	$ 3.56	$ 0.86	$ 0.07
Diluted earnings per unit:
Loss from continuing operations available to common stockholders per common share-diluted (Note 19)																	$ (0.24)	$ (0.36)	$ (0.33)
Income from discontinued operations per common unit																	$ 3.80	$ 1.22	$ 0.40
Net income available to common unitholders per unit-diluted (Note 20)	$ 2.44	[3]	$ (0.04)	[3]	$ (0.02)	[3]	$ 1.05	[3]	$ 0.68	[3]	$ 0.17	[3]	$ (0.01)	[3]	$ 0.01	[3]	$ 3.56	$ 0.86	$ 0.07
Market Measure-Based Restricted Stock Units (RSUs) [Member]
Diluted earnings per unit:
Number of RSUs outstanding	88,490																88,490

[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] 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.

[3] 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.