Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income available to common unitholders	$ 19,618	$ 42,194	$ 59,435	$ 79,097
Allocation to participating securities	(542)	(543)	(1,085)	(1,052)
Numerator for basic and diluted net income available to common stockholders	$ 19,076	$ 41,651	$ 58,350	$ 78,045
Denominator:
Basic weighted average vested shares outstanding (in shares)	115,084,897	100,972,355	110,980,066	100,937,069
Effect of dilutive securities (in shares)	454,828	837,186	484,581	681,884
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	115,539,725	101,809,541	111,464,647	101,618,953
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.17	$ 0.41	$ 0.53	$ 0.77
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.17	$ 0.41	$ 0.52	$ 0.77
Kilroy Realty L.P. [Member]
Numerator:
Net income available to common unitholders	$ 19,838	$ 42,901	$ 60,227	$ 80,409
Allocation to participating securities	(542)	(543)	(1,085)	(1,052)
Numerator for basic and diluted net income available to common stockholders	$ 19,296	$ 42,358	$ 59,142	$ 79,357
Denominator:
Basic weighted average vested shares outstanding (in shares)	117,098,562	102,995,642	112,997,795	102,960,599
Effect of dilutive securities (in shares)	454,828	837,186	484,581	681,884
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	117,553,390	103,832,828	113,482,376	103,642,483
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.16	$ 0.41	$ 0.52	$ 0.77
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.16	$ 0.41	$ 0.52	$ 0.77