Unsecured Senior Notes (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Unsecured debt	$ 1,431,217,000		$ 1,431,132,000
Exchangeable senior notes, net	169,528,000		168,372,000
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt	1,431,217,000		1,431,132,000
Exchangeable senior notes, net	169,528,000		168,372,000
Kilroy Realty, L.P. [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Contingent Additional Borrowings	200,000,000
Debt Instrument, Basis Spread on Variable Rate	1.45%
Kilroy Realty, L.P. [Member] | Three Point Eight Zero Zero Percent Unsecured Senior Note [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	299,913,000		299,910,000
Stated coupon rate	3.80%
Debt Instrument, Unamortized Discount	(87,000)		(90,000)
Debt Instrument, Interest Rate, Effective Percentage	3.804%	[1],[2]
Debt Instrument, Face Amount	300,000,000		300,000,000
Kilroy Realty, L.P. [Member] | Exchangeable Note Two [Member] | Exchangeable Debt [Member]
Debt Instrument [Line Items]
Minimum percentage of exchange price	130.00%
Debt Instrument, Convertible, Number of Equity Instruments	4,800,796	[3]
Debt Instrument, Convertible, Conversion Ratio	27.8307	[3]
Debt Instrument, Convertible, Stock Price Trigger	$ 35.93	[3]
Debt Instrument, Convertible, Carrying Amount of Equity Component	19,835,000
Principal amount	172,500,000		172,500,000
Stated coupon rate	4.25%	[4]
Debt Instrument, Unamortized Discount	2,972,000		4,128,000
Debt Instrument, Interest Rate, Effective Percentage	7.13%	[5]
Kilroy Realty, L.P. [Member] | Exchangeable Note Two [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Exchangeable senior notes, net	169,528,000		168,372,000
Kilroy Realty, L.P. [Member] | Six Point Four Five Percent Unsecured Senior Notes due Aug 4 2014 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	83,000,000		83,000,000
Maturity Date	Aug. 04, 2014
Stated coupon rate	6.45%
Debt Instrument, Interest Rate, Effective Percentage	6.45%
Kilroy Realty, L.P. [Member] | One Hundred Fifty Million Term Loan Facility [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Contingent Additional Borrowings	100,000,000
Unsecured debt	150,000,000		150,000,000
Debt Instrument, Basis Spread on Variable Rate	1.75%
Kilroy Realty, L.P. [Member] | Four Point Eight Percent Unsecured Senior Notes Due July Fifteen Two Thousand Eighteen [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	324,680,000		324,661,000
Stated coupon rate	4.80%
Debt Instrument, Unamortized Discount	(320,000)		(339,000)
Debt Instrument, Interest Rate, Effective Percentage	4.827%	[1],[6]
Debt Instrument, Face Amount	325,000,000		325,000,000
Kilroy Realty, L.P. [Member] | Six Point Six Two Five Percent Unsecured Senior Notes due June 1 2020 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	248,687,000		248,633,000
Stated coupon rate	6.625%
Debt Instrument, Unamortized Discount	(1,313,000)		(1,367,000)
Debt Instrument, Interest Rate, Effective Percentage	6.743%	[1],[7]
Debt Instrument, Face Amount	250,000,000		250,000,000
Kilroy Realty, L.P. [Member] | Five Percent Unsecured Senior Notes due Nov3 2015 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	324,937,000		324,927,000
Stated coupon rate	5.00%
Debt Instrument, Unamortized Discount	(63,000)		(73,000)
Debt Instrument, Interest Rate, Effective Percentage	5.014%	[1],[8]
Debt Instrument, Face Amount	$ 325,000,000		$ 325,000,000

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

[2] Interest on the 3.800% unsecured senior notes is payable semi-annually in arrears on January 15th and July 15th of each year.

[3] 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.

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

[5] 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.

[6] Interest on the 4.800% unsecured senior notes is payable semi-annually in arrears on January 15th and July 15th of each year.

[7] Interest on the 6.625% unsecured senior notes is payable semi-annually in arrears on June 1st and December 1st of each year.

[8] Interest on the 5.000% unsecured senior notes is payable semi-annually in arrears on May 3rd and November 3rd of each year.