Net Income Available to Common Stockholders Per Share of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income attributable to Kilroy Realty Corporation	$ 43,846	$ 34,400	$ 122,943	$ 98,195
Allocation to participating securities	(530)	(507)	(1,582)	(1,492)
Numerator for basic and diluted net income available to common stockholders	$ 43,316	$ 33,893	$ 121,361	$ 96,703
Denominator:
Basic weighted average vested shares outstanding (in shares)	104,841,176	100,676,778	102,252,739	99,711,312
Effect of dilutive securities (in shares)	518,728	551,556	619,697	497,333
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	105,359,904	101,228,334	102,872,436	100,208,645
Basic earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.34	$ 1.19	$ 0.97
Diluted earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 0.41	$ 0.33	$ 1.18	$ 0.97