Dispositions (Details) $ in Thousands			3 Months Ended		9 Months Ended
		Jan. 15, 2015 USD ($)	Sep. 30, 2015 USD ($) ft² building	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) ft² building	Sep. 30, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings			10		10
Net Rentable Area | ft²			1,046,394		1,046,394
Dispositions Sales Price | $					$ 309,200
Gains on sales of depreciable operating properties | $			$ 78,522	$ 0	109,950	$ 0
Gain on sale of land | $			$ 0	$ 0	$ 17,268	$ 3,490
15050 NE 36th Street, Redmond, WA [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings			1		1
Net Rentable Area | ft²			122,103		122,103
San Diego Properties Phase I [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings	[1]		3		3
Net Rentable Area | ft²	[1]		384,468		384,468
San Diego Properties Phase 2 [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings	[2]		6		6
Net Rentable Area | ft²	[2]		539,823		539,823
Properties Held for Sale [Member] | Von Karman, Irvine, California [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Dispositions Sales Price | $		$ 26,000

[1] (1)The San Diego Properties - Tranche 1 include the following: 10770 Wateridge Circle, 6200 Greenwich Drive, and 6220 Greenwich Drive.

[2] (2)The San Diego Properties - Tranche 2 include the following: 6260 Sequence Drive, 6290 Sequence, Drive, 6310 Sequence Drive, 6340 Sequence Drive, 6350 Sequence Drive, and 4921 Directors Place.