Partners' Capital of the Operating Partnership (Details) - shares	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
General Partners' Capital Account [Abstract]
Ownership interest of noncontrolling interest	2.00%	2.00%	2.10%
Operating Partnership [Member]
General Partners' Capital Account [Abstract]
Company owned general partnership interest	98.00%	98.00%	97.90%
Kilroy Realty L.P. [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Company owned common units in the Operating Partnership	100,967,024	100,746,988	98,839,708
Noncontrolling common units of the Operating Partnership	2,023,287	2,025,287	2,070,690