Dispositions and Real Estate Assets Held for Sale - Land Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) a	Dec. 31, 2015 USD ($) a	Dec. 31, 2014 USD ($) a
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Secured debt assumed by buyers in connection with land disposition	$ 2,322	$ 0	$ 0
Net (loss) gain on sales of land	$ (295)	17,116	$ 3,490
Carlsbad Oaks - Lot 7 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	7.6
Dispositions sales price	$ 4,500
Gain (loss) on sale of properties		$ (200)
Carlsbad Oaks - Lots 4 & 5 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	11.2
Dispositions sales price	$ 6,000
Carlsbad Oaks - Lot 8 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	13.2
Dispositions sales price	$ 8,900
Carlsbad Oaks - Lots 7, 4 & 5, 8 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	32.0
Dispositions sales price	$ 19,400
Von Karman, Irvine, California [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a		8.5
Dispositions sales price		$ 26,000
Gain (loss) on sale of properties		17,300
10850 Via Frontera San Diego CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a			21.0
Dispositions sales price			$ 33,100
4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	7.0
Kilroy Realty, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Secured debt assumed by buyers in connection with land disposition	$ 2,322	0	0
Net (loss) gain on sales of land	$ (295)	$ 17,116	$ 3,490