Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income available to common unitholders	$ 47,028	$ 49,028	$ 580,498	$ 108,463
Allocation to participating securities	(388)	(572)	(1,124)	(1,657)
Numerator for basic and diluted net income available to common stockholders	$ 46,640	$ 48,456	$ 579,374	$ 106,806
Denominator:
Basic weighted average vested shares outstanding (in shares)	116,456,796	115,226,324	116,418,113	112,405,817
Effect of dilutive securities (in shares)	505,884	441,333	476,321	470,058
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	116,962,680	115,667,657	116,894,434	112,875,875
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.40	$ 0.42	$ 4.98	$ 0.95
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.40	$ 0.42	$ 4.96	$ 0.95
Kilroy Realty L.P. [Member]
Numerator:
Net income available to common unitholders	$ 47,488	$ 49,728	$ 586,198	$ 109,955
Allocation to participating securities	(388)	(572)	(1,124)	(1,657)
Numerator for basic and diluted net income available to common stockholders	$ 47,100	$ 49,156	$ 585,074	$ 108,298
Denominator:
Basic weighted average vested shares outstanding (in shares)	117,607,370	117,158,160	117,568,687	114,394,706
Effect of dilutive securities (in shares)	505,884	441,333	476,321	470,058
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	118,113,254	117,599,493	118,045,008	114,864,764
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.40	$ 0.42	$ 4.98	$ 0.95
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.40	$ 0.42	$ 4.96	$ 0.94