Dispositions and Real Estate Assets Held for Sale - Operating Properties Held for Sale (Details) $ in Millions	1 Months Ended
	Jan. 31, 2017 USD ($)	Jan. 31, 2016 USD ($)	Dec. 31, 2016 ft² building property	Dec. 31, 2015 ft² property	Jan. 31, 2014 ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet (unaudited)			14,025,856		79,000
Torrey Santa Fe Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property			4
Rentable Square Feet (unaudited)			465,812
Properties held for sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property			1
Rentable Square Feet (unaudited)			67,995
Properties held for sale [Member] | Pacific Center Boulevard, Sorrento Mesa, California [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | building			1
Rentable Square Feet (unaudited)			67,995
Properties held for sale [Member] | Torrey Santa Fe Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property				4
Rentable Square Feet (unaudited)				465,812
Dispositions sales price | $		$ 262.3
Subsequent event [Member] | Properties held for sale [Member] | Pacific Center Boulevard, Sorrento Mesa, California [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Dispositions sales price | $	$ 12.1