Net Income Available to Common Stockholders Per Share of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income attributable to Kilroy Realty Corporation	$ 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 shares)	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 share:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36
Diluted earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.36