Partners' Capital of the Operating Partnership (Details) - shares	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Operating Partnership [Member]
General Partners' Capital Account [Abstract]
Ownership interest (percent)	98.30%	98.00%	98.10%
Kilroy Realty L.P. [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Company owned common units in the Operating Partnership (in units)	115,176,538	100,972,035	106,016,287
Noncontrolling common units of the Operating Partnership (in units)	1,934,586		2,023,287
Non-affiliated investors and certain of our executive officers and directors [Member] | Operating Partnership [Member]
General Partners' Capital Account [Abstract]
Ownership interest (percent)	1.70%	2.00%	1.90%
Non-affiliated investors and certain of our executive officers and directors [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Noncontrolling common units of the Operating Partnership (in units)	1,934,586	2,023,287	2,023,287