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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 42,194	$ 27,549	$ 79,097	$ 63,795
Allocation to participating securities	(543)	(514)	(1,052)	(985)
Numerator for basic and diluted net income available to common stockholders	$ 41,651	$ 27,035	$ 78,045	$ 62,810
Denominator:
Basic weighted average vested shares outstanding (in shares)	100,972,355	99,691,700	100,937,069	99,220,577
Effect of dilutive securities (in units)	837,186	459,156	681,884	467,105
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	101,809,541	100,150,856	101,618,953	99,687,682
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.27	$ 0.77	$ 0.63
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.27	$ 0.77	$ 0.63
Kilroy Realty L.P. [Member]
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 42,901	$ 28,015	$ 80,409	$ 64,908
Allocation to participating securities	(543)	(514)	(1,052)	(985)
Numerator for basic and diluted net income available to common stockholders	$ 42,358	$ 27,501	$ 79,357	$ 63,923
Denominator:
Basic weighted average vested shares outstanding (in shares)	102,995,642	101,762,390	102,960,599	101,291,549
Effect of dilutive securities (in units)	837,186	459,156	681,884	467,105
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	103,832,828	102,221,546	103,642,483	101,758,654
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.27	$ 0.77	$ 0.63
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.27	$ 0.77	$ 0.63