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
	Mar. 31, 2013		Mar. 31, 2012	Dec. 31, 2012
Numerator:
Income from continuing operations	$ 2,388		$ 2,165
Total preferred distributions	(3,313)		(9,336)
Allocation to participating securities (nonvested units and time-based RSUs)	(418)		(380)
Numerator for basic and diluted loss from continuing operations available to common unitholders	(1,321)		(7,365)
Income from discontinued operations	0		76,506
Numerator for basic and diluted net (loss) income available to common unitholders	(1,321)		67,160
Denominator:
Weighted average common units outstanding - basic (Note 13)	74,977,240		63,648,704
Effect of dilutive securities - contingently issuable shares and stock options	0		0
Weighted average common units outstanding - diluted (Note 13)	74,977,240		63,648,704
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 13)	$ (0.02)		$ (0.12)
Income from discontinued operations per common unit	$ 0.00		$ 1.18
Net (loss) income available to common unitholders per unit-basic (Note 13)	$ (0.02)		$ 1.06
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 13)	$ (0.02)		$ (0.12)
Income from discontinued operations per common unit	$ 0.00		$ 1.18
Net (loss) income available to common unitholders per unit-diluted (Note 13)	$ (0.02)		$ 1.06
Stock options outstanding	1,528,000	[1],[2]	1,550,000	1,540,000
Kilroy Realty, L.P. [Member]
Numerator:
Income from continuing operations	2,388		2,165
Income from continuing operations attributable to noncontrolling interests in consolidated subsidiaries	(69)		(53)
Total preferred distributions	(3,313)		(9,336)
Allocation to participating securities (nonvested units and time-based RSUs)	(418)		(380)
Numerator for basic and diluted loss from continuing operations available to common unitholders	(1,412)		(7,604)
Income from discontinued operations	0		76,506
Numerator for basic and diluted net (loss) income available to common unitholders	$ (1,412)		$ 68,902
Denominator:
Weighted average common units outstanding - basic (Note 13)	76,803,743		65,366,835
Effect of dilutive securities - contingently issuable shares and stock options	0		0
Weighted average common units outstanding - diluted (Note 13)	76,803,743		65,366,835
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 13)	$ (0.02)		$ (0.12)
Income from discontinued operations per common unit	$ 0.00		$ 1.17
Net (loss) income available to common unitholders per unit-basic (Note 13)	$ (0.02)		$ 1.05
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 13)	$ (0.02)		$ (0.12)
Income from discontinued operations per common unit	$ 0.00		$ 1.17
Net (loss) income available to common unitholders per unit-diluted (Note 13)	$ (0.02)		$ 1.05
Stock options outstanding	1,528,000		1,550,000
Market Measure-Based Restricted Stock Units (RSUs) [Member]
Diluted earnings per unit:
Market measure-based RSUs			103,239
Market Measure-Based Restricted Stock Units (RSUs) [Member] | Kilroy Realty, L.P. [Member]
Diluted earnings per unit:
Market measure-based RSUs	88,491		103,239

[1] As of March 31, 2013, 308,000 of the outstanding stock options were exercisable.

[2] The total intrinsic value of options outstanding at March 31, 2013 was $15.0 million.