Organization and Basis of Presentation (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) ft² project tenant building property
Real Estate Properties [Line Items]
Number of buildings | building	10
Rentable square feet	1,046,394
Dispositions Sales Price | $	$ 309.2
Kilroy Realty Finance, Inc. [Member]
Real Estate Properties [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	1.00%
Lease Up Properties [Member]
Real Estate Properties [Line Items]
Number of buildings | project	1
Rentable square feet	108,539
Development Properties [Member]
Real Estate Properties [Line Items]
Number of buildings | project	7	[1]
Rentable square feet	2,322,000	[1]
Office Properties [Member]
Real Estate Properties [Line Items]
Number of buildings | building	101
Rentable square feet	13,050,947
Number of Tenants | tenant	509
Percentage Occupied	95.60%
WASHINGTON
Real Estate Properties [Line Items]
Number of buildings | property	12
Development Properties [Domain]
Real Estate Properties [Line Items]
Number of buildings | project	10

[1] Estimated rentable square feet upon completion.