Dispositions and Real Estate Assets Held for Sale - Operating Property Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) ft² a property	Dec. 31, 2015 USD ($) ft² property	Dec. 31, 2014 USD ($) 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) | ft²	14,025,856			79,000
Gains on sales of depreciable operating properties | $	$ 164,302	$ 109,950	$ 0
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) | ft²	465,812
Proceeds from sale of property held-for-sale | $	$ 262,300
4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property	2
Rentable Square Feet (unaudited) | ft²	136,908
Proceeds from sale of property held-for-sale | $	$ 49,000
Area of land | a	7.0
Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property	6
Rentable Square Feet (unaudited) | ft²	602,720
Proceeds from sale of property held-for-sale | $	$ 311,300
15050 N.E. 36th St., Redmond, WA [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) | ft²		122,103
Proceeds from sale of property held-for-sale | $		$ 51,200
San Diego Properties Tranches 1 & 2, San Diego, CA [Member] [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property		9
Rentable Square Feet (unaudited) | ft²		924,291
Proceeds from sale of property held-for-sale | $		$ 258,000
15050 NE 36th Street, Redmond, WA & San Diego Properties - Tranches 1 and 2 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property		10
Rentable Square Feet (unaudited) | ft²		1,046,394
Proceeds from sale of property held-for-sale | $		$ 309,200
San Diego Properties, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property			12
Rentable Square Feet (unaudited) | ft²			1,049,035
Proceeds from sale of property held-for-sale | $			$ 294,700
9785&9791 Towne Centre Drive, San Diego CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property			2
Rentable Square Feet (unaudited) | ft²			126,000
Proceeds from sale of property held-for-sale | $			$ 29,500
111 Pacifica [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) | ft²			67,496
Proceeds from sale of property held-for-sale | $			$ 15,100
4040 Civic [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) | ft²			130,237
Proceeds from sale of property held-for-sale | $			$ 34,900
999 Town &Country [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) | ft²			98,551
Proceeds from sale of property held-for-sale | $			$ 25,300
Torrey Santa Fe Properties and 490, 4939, & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property	6
San Diego Properties, San Diego, CA & 9785 & 9791 Towne Centre Drive, San Diego, CA & 111 Pacifica, Irvine, CA & 4040 Civic Center Drive, San Rafael, CA & 999 Town & Country Road, Orange, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings | property			17
Rentable Square Feet (unaudited) | ft²			1,471,319
Proceeds from sale of property held-for-sale | $			$ 399,500