Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 36,903	$ 36,246
Allocation to participating securities	(509)	(471)
Numerator for basic and diluted net income available to common stockholders	$ 36,394	$ 35,775
Denominator:
Basic weighted average vested shares outstanding (in shares)	100,901,390	98,744,220
Effect of dilutive securities (in units)	541,789	469,390
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	101,443,179	99,213,610
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36
Kilroy Realty L.P. [Member]
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 37,508	$ 36,893
Allocation to participating securities	(509)	(471)
Numerator for basic and diluted net income available to common stockholders	$ 36,999	$ 36,422
Denominator:
Basic weighted average vested shares outstanding (in shares)	102,925,166	100,815,477
Effect of dilutive securities (in units)	541,789	469,390
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	103,466,955	101,284,867
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36