Secured and Unsecured Debt of the Operating Partnership (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Secured Debt	$ 556,946	[1]	$ 560,434	[1]
Secured Debt [Member] | 4.48% Mortgage Payable due July 1, 2027 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.48%	[2]
Effective interest rate	4.48%	[2],[3]
Maturity Date	Jul. 01, 2027
Secured Debt	97,000	[1],[4]	97,000	[1],[4]
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Secured Debt	556,946		560,434
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 4.27% Mortgage Payable due Feb. 01, 2018 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.27%	[2]
Effective interest rate	4.27%	[2],[3]
Maturity Date	Feb. 01, 2018
Secured Debt	132,539	[1]	133,117	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	6.05%	[2]
Effective interest rate	3.50%	[2],[3]
Maturity Date	Jun. 01, 2019
Secured Debt	91,696	[1],[4]	92,502	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.51% Mortgage Payable due Feb. 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	6.51%	[2]
Effective interest rate	6.51%	[2],[3]
Maturity Date	Feb. 01, 2017
Secured Debt	67,415	[1]	67,663	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.23% Mortgage Payable due Jan. 01, 2016 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.23%	[2]
Effective interest rate	3.50%	[2],[3]
Maturity Date	Jan. 01, 2016
Secured Debt	54,120	[1],[4]	54,570	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.57% Morgage Payable Due Feb. 11, 2016 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.57%	[2]
Effective interest rate	3.25%	[2],[3]
Maturity Date	Feb. 11, 2016
Secured Debt	41,300	[1],[4]	41,654	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.09% Mortgage Payable due Aug. 7, 2015 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.09%	[2]
Effective interest rate	3.50%	[2],[3]
Maturity Date	Aug. 07, 2015
Secured Debt	34,712	[1],[4]	34,845	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 4.94% Mortgage Payable due April 15, 2015 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.94%	[2]
Effective interest rate	4.00%	[2],[3]
Maturity Date	Apr. 15, 2015
Secured Debt	27,307	[1],[4]	27,641	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 7.15% Mortgage Payable due May 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	7.15%	[2]
Effective interest rate	7.15%	[2],[3]
Maturity Date	May 01, 2017
Secured Debt	8,387	[1]	8,972	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | Municipal Bonds [Member]
Debt Instrument [Line Items]
Secured Debt	$ 2,470	[1]	$ 2,470	[1]

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

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

[3] 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.

[4] The secured debt and the related properties that secure the debt are held in a special purpose entity and the properties are not available to satisfy the debts and other obligations of the Company or the Operating Partnership.