Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) $ / shares in Units, $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) trading_day $ / shares shares	Jun. 30, 2019 shares	Dec. 31, 2019 USD ($) $ / shares shares
Noncontrolling Interest [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Number of trading days | trading_day	10
Aggregate value upon redemption of outstanding noncontrolling common units | $	$ 118.0		$ 167.7
Non-affiliated investors and certain of our executive officers and directors [Member] | Common units [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in units)	1,934,586	2,023,287	2,023,287
Kilroy Realty L.P. [Member] | Common units [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in units)	1,934,586		2,023,287
Operating Partnership [Member]
Noncontrolling Interest [Line Items]
Ownership interest (percent)	98.30%	98.00%	98.10%
Operating Partnership [Member] | Non-affiliated investors and certain of our executive officers and directors [Member]
Noncontrolling Interest [Line Items]
Ownership interest (percent)	1.70%	2.00%	1.90%