Organization and Basis of Presentation (Details Textuals) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 building entity		Sep. 30, 2013 building entity		Sep. 30, 2012	Dec. 31, 2012 entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Stabilized Occupancy	95.00%
Percentage of general partnership interest owned by the company in the Operating Partnership	97.80%		97.80%		97.60%	97.60%
Percentage of Common limited partnership interest owned by certain non-affiliated investors and certain directors and officers of the Company in the Operating Partnership	2.20%		2.20%		2.40%	2.40%
Number of buildings	14		14
Number of VIE's	2		2			2
VIE Assets	$ 135,300,000		$ 135,300,000			$ 337,000,000
VIE Liabilities	4,100,000		4,100,000			111,100,000
Impact of VIE to Noncontrolling interest	4,885,000		4,885,000			0
Restricted cash	228,300,000		229,613,000		(5,526,000)
WASHINGTON
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	11		11
Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of General partnership interest owned by wholly-owned subsidiary of the Company			1.00%
Percentage of limited partnership interest owned by Operating Partnership	99.00%
Properties Held for Sale [Member] | Other Segments [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	14	[1]	14	[1]
Properties Held for Sale [Member] | Other Segments [Member] | San Diego, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	13	[2],[3]	13	[2],[3]
Properties Held for Sale [Member] | Other Segments [Member] | Anaheim, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	1	[2],[4]	1	[2],[4]
Real Estate Investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE Assets	$ 119,262,000		$ 119,262,000			$ 319,770,000

[1] Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).

[2] Estimated rentable square feet upon completion.

[3] The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.

[4] We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.