Secured and Unsecured Debt of the Operating Partnership (Details 1) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Debt Instrument [Line Items]
Unsecured debt	$ 1,431,217,000			$ 1,431,132,000
Balance and significant terms of the Exchangeable Notes outstanding
Net carrying amount of liability component	169,528,000			168,372,000
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange Abstract
Average trading price of the Companys stock	$ 55.18		$ 51.14
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt	1,431,217,000			1,431,132,000
Balance and significant terms of the Exchangeable Notes outstanding
Net carrying amount of liability component	169,528,000			168,372,000
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Maturity Date	Jun. 01, 2019
Stated coupon rate	6.05%	[1]
Effective interest rate	3.50%	[1],[2]
Kilroy Realty, L.P. [Member] | Exchangeable Notes [Member]
Interest Expense for the Exchangeable Notes
Contractual interest payments	1,833,000		1,833,000
Amortization of discount	1,156,000		1,078,000
Interest expense attributable to the Exchangeable Notes	2,989,000		2,911,000
Kilroy Realty, L.P. [Member] | Exchangeable Notes [Member] | 4.25% Exchangeable Notes [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Net carrying amount of liability component	169,528,000			168,372,000
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange Abstract
Fair Value Of Shares Upon Conversion If Exchangeable Notes Were Converted On Specified Date	270,602,000		247,300,000
Debt Instrument, Convertible, If-converted Value in Excess of Principal	98,102,000		74,800,000
Capped call transactions
Referenced shares of common stock	4,800,796
Exchange price including effect of capped calls	42.81
Kilroy Realty, L.P. [Member] | Exchangeable Debt [Member] | 4.25% Exchangeable Notes [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Principal amount	172,500,000			172,500,000
Unamortized discount	(2,972,000)			(4,128,000)
Carrying amount of equity component	$ 19,835,000
Stated coupon rate	4.25%	[3]
Effective interest rate	7.13%	[4]
Exchange rate per $1,000 principal value of the Exchangeable Notes, as adjusted	27.8307	[5]
Exchange price, as adjusted	$ 35.93	[5]
Number of Shares on which aggregate consideration to be delivered upon conversion is determined	4,800,796	[5]
Minimum percentage of exchange price	130.00%

[1] All interest rates presented are fixed-rate interest rates.

[2] This represents the rate at which interest expense is recorded for financial reporting purposes, which reflects the amortization of discounts/premiums, excluding debt issuance costs.

[3] Interest on the 4.25% Exchangeable Notes is payable semi-annually in arrears on May 15th and November 15th of each year.

[4] The rate at which we record interest expense for financial reporting purposes, which reflects the amortization of the discounts on the 4.25% Exchangeable Notes. This rate represents our conventional debt borrowing rate at the date of issuance.

[5] The exchange rate, exchange price and the number of shares to be delivered upon conversion are subject to adjustment under certain circumstances including increases in our common dividends.