Partners’ Capital of the Operating Partnership (Details) - $ / shares	1 Months Ended	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
General Partners' Capital Account [Abstract]
Company owned general partnership interest (percentage)	97.20%	97.20%	98.10%	98.00%
Ownership interest of noncontrolling interest (percentage)	2.80%	2.80%	1.90%	2.00%
Kilroy Realty, L.P. [Member] | Capital Units [Member]
General Partners' Capital Account [Abstract]
Company owned common units in the Operating Partnership	92,229,464	92,229,464	92,258,690	88,031,377
Noncontrolling common units of the Operating Partnership	2,631,276	2,631,276	1,764,775	1,793,170
Brannan St Project [Member]
Class of Stock [Line Items]
Common units issued	867,701	867,701
Value per common unit issued	$ 55.36	$ 55.36
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01