Secured Debt (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Secured Debt	$ 516,725,000	[1]	$ 546,292,000	[1]
Secured Debt [Member]
Debt Instrument [Line Items]
Unamortized premium	9,200,000		10,300,000
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Secured Debt	516,725,000		546,292,000
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	130,164,000	[1]	130,767,000	[1]
Kilroy Realty, L.P. [Member] | 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	97,000,000	[1],[4]	97,000,000	[1],[4]
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	88,411,000	[1],[4]	89,242,000	[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	66,383,000	[1]	66,647,000	[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	52,332,000	[1],[4]	52,793,000	[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	39,895,000	[1],[4]	40,258,000	[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	34,178,000	[1],[4]	34,311,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | Four Point Nine four Percent Mortgage Payable due April Fifteen Two Thousand Fifteen [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	0	[1],[5]	26,285,000	[1],[5]
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	5,940,000	[1]	6,568,000	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | Municipal Bonds [Member]
Debt Instrument [Line Items]
Secured Debt	$ 2,422,000	[1]	$ 2,421,000	[1]

[1] Amounts reported include the amounts of unamortized debt premiums of $9.2 million and $10.3 million as of March 31, 2015 and December 31, 2014, respectively.

[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.

[5] This mortgage note payable was repaid during the three months ended March 31, 2015 prior to maturity at par.