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				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Numerator:
Income (loss) from continuing operations	$ 2,683		$ (2,167)		$ 10,289		$ (4,941)
Total preferred distributions	(3,312)		(5,342)		(9,938)		(17,775)
Allocation to participating securities	(450)	[1]	(408)	[1]	(1,292)	[1]	(1,225)	[1]
Numerator for basic and diluted loss from continuing operations available to common unitholders	(1,065)		(7,738)		(949)		(23,377)
Income from discontinued operations	6,344		4,689		11,229		88,412
Numerator for basic and diluted net income (loss) available to common unitholders	5,134		(3,161)		10,022		62,763
Denominator:
Weighted average common units outstanding - basic (Note 14)	76,768,893		71,889,475		75,750,822		67,975,309
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common units outstanding - diluted (Note 14)	76,768,893		71,889,475		75,750,822		67,975,309
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	$ (0.01)		$ (0.10)		$ (0.01)		$ (0.34)
Income from discontinued operations per common unit	$ 0.08		$ 0.06		$ 0.14		$ 1.26
Net income (loss) available to common unitholders per unit-basic (Note 14)	$ 0.07		$ (0.04)		$ 0.13		$ 0.92
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	$ (0.01)		$ (0.10)		$ (0.01)		$ (0.34)
Income from discontinued operations per common unit	$ 0.08		$ 0.06		$ 0.14		$ 1.26
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$ 0.07		$ (0.04)		$ 0.13		$ 0.92
Stock options outstanding	1,525,000		1,540,000		1,525,000		1,540,000
Kilroy Realty, L.P. [Member]
Numerator:
Income (loss) from continuing operations	2,683		(2,167)		10,289		(4,941)
Income from continuing operations attributable to noncontrolling interests in consolidated subsidiaries	(47)		(48)		(178)		(144)
Total preferred distributions	(3,312)		(5,342)		(9,938)		(17,775)
Allocation to participating securities	450	[1]	408	[1]	1,292	[1]	1,225	[1]
Numerator for basic and diluted loss from continuing operations available to common unitholders	(1,126)		(7,965)		(1,119)		(24,085)
Income from discontinued operations	6,344		4,689		11,229		88,412
Numerator for basic and diluted net income (loss) available to common unitholders	$ 5,218		$ (3,276)		$ 10,110		$ 64,327
Denominator:
Weighted average common units outstanding - basic (Note 14)	78,590,396		73,680,259		77,574,907		69,717,834
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common units outstanding - diluted (Note 14)	78,590,396		73,680,259		77,574,907		69,717,834
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	$ (0.01)		$ (0.10)		$ (0.01)		$ (0.34)
Income from discontinued operations per common unit	$ 0.08		$ 0.06		$ 0.14		$ 1.26
Net income (loss) available to common unitholders per unit-basic (Note 14)	$ 0.07		$ (0.04)		$ 0.13		$ 0.92
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	$ (0.01)		$ (0.10)		$ (0.01)		$ (0.34)
Income from discontinued operations per common unit	$ 0.08		$ 0.06		$ 0.14		$ 1.26
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$ 0.07		$ (0.04)		$ 0.13		$ 0.92
Market Measure-Based Restricted Stock Units (RSUs) [Member] | Kilroy Realty, L.P. [Member]
Diluted earnings per unit:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements, Restricted Stock Units	159,360		103,238		159,360		103,238

[1] Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.