CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	115,067,924	106,016,287
Common stock, shares outstanding (in shares)	115,067,924	106,016,287
Common units [Member] | Kilroy Realty L.P. [Member]
General partner, units issued	115,067,924	106,016,287
General partners, units outstanding	115,067,924	106,016,287
Limited partners, units issued	2,021,287	2,023,287
Noncontrolling common units of the Operating Partnership	2,021,287	2,023,287