Organization and Basis of Presentation (Details Textuals) $ in Thousands	3 Months Ended
	Mar. 31, 2016 ft²	Mar. 31, 2016	Mar. 31, 2016 project	Mar. 31, 2016 a	Mar. 31, 2016 USD ($)	Mar. 31, 2016 building	Mar. 31, 2016 variable_interest_entity	Mar. 31, 2016 property	Dec. 31, 2015 USD ($) variable_interest_entity	Mar. 31, 2015
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Lease-up properties occupancy percentage	95.00%
Common general partnership interest in the Operating Partnership (percentage)		97.20%							98.10%	98.00%
Common limited partnership interest in the Operating Partnership (percentage)		2.80%							1.90%	2.00%
Number of VIEs | variable_interest_entity							2		2
VIE assets					$ 208,300				$ 203,300
VIE liabilities					26,300				28,800
Noncontrolling interest in VIE					6,715				6,520
Kilroy Realty Finance, Inc. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common general partnership interest in the Finance Partnership (percentage)	1.00%
Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of limited partnership interest owned by Operating Partnership	99.00%
Redwood LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of VIEs | variable_interest_entity							1
Development Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | project			2
Rentable square feet | ft²	905,000
Development Properties [Member] | San Francisco, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | building						2
Development Properties [Member] | San Francisco, California [Member] | Development Project One [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Rentable square feet | ft²	455,340
Development Properties [Member] | San Francisco, California [Member] | Development Project Two [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Rentable square feet | ft²	185,602
Development Properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property								1
Lease Up Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | project			2
Rentable square feet | ft²	443,000
Office Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties			10			103
Rentable square feet | ft²	13,671,730
Area of land | a				101
Office Properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property								12
Properties and Development Projects [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property ownership percentage	100.00%
Real Estate Held-for-investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE assets					$ 187,300				187,300
Prepaid Expenses and Other Current Assets [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Deferred financing costs									4,600
Secured Debt, net [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Deferred financing costs									1,100
Unsecured Debt, Net [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Deferred financing costs									$ 12,000