Secured and Unsecured Debt of the Company Secured and Unsecured Debt of the Company (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Unsecured Debt	$ 1,130,895,000		$ 980,569,000
Secured Debt	561,096,000		351,825,000
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured Debt	1,130,895,000		980,569,000
Secured Debt	561,096,000		351,825,000
Maximum dividend payment as percentage of funds from operations	95.00%
Kilroy Realty, L.P. [Member] | Unsecured Term Loan [Member] | One Hundred Fifty Million Term Loan Facility [Member]
Debt Instrument [Line Items]
Unsecured Debt	150,000,000
Kilroy Realty, L.P. [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt			1,500,000,000
Kilroy Realty, L.P. [Member] | Unsecured Senior Notes [Member] | 6.625% Unsecured Senior Notes due June 1, 2020 [Member]
Debt Instrument [Line Items]
Unsecured Debt	248,420,000		248,207,000
Stated interest rate	6.625%	[1]
Kilroy Realty, L.P. [Member] | Unsecured Senior Notes [Member] | 4.80% Unsecured Senior Notes due July 15, 2018 [Member]
Debt Instrument [Line Items]
Unsecured Debt	324,587,000		324,514,000
Stated interest rate	4.80%	[2]
Kilroy Realty, L.P. [Member] | Unsecured Senior Notes [Member] | 5.00% Unsecured Senior Notes due Nov 3, 2015 [Member]
Debt Instrument [Line Items]
Unsecured Debt	324,888,000		324,848,000
Stated interest rate	5.00%	[3]
Kilroy Realty, L.P. [Member] | Unsecured Senior Notes [Member] | 6.45% Unsecured Senior Notes due Aug 4 2014 [Member]
Debt Instrument [Line Items]
Unsecured Debt	83,000,000
Stated interest rate	6.45%
Kilroy Realty, L.P. [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Borrowing capacity	500,000,000	[4]	500,000,000	[4]
Kilroy Realty, L.P. [Member] | Exchangeable Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.25%
Kilroy Realty, L.P. [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Secured Debt	$ 561,096,000	[5]	$ 351,825,000	[5]

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

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

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

[4] We may elect to borrow, subject to bank approval, up to an additional $200.0 million under an accordion feature under the terms of the revolving credit facility.

[5] Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.