Acquisitions (Details) $ in Thousands		9 Months Ended
		Sep. 30, 2015 USD ($) ft² building	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Payments to Acquire Land		$ 127,500
Number of buildings | building		10
Rentable square feet | ft²		1,046,394
Liabilities
Accounts Payable and Accrued Liabilities		$ 249,980	$ 225,830
Dexter Project [Member] [Member]
Business Acquisition [Line Items]
Accrued Liabilities and Acquisition Costs	[1],[2]	2,400
Payments to Acquire Land	[1]	49,500
Hooper Project [Member] [Member] [Domain]
Business Acquisition [Line Items]
Accrued Liabilities and Acquisition Costs		4,100
Payments to Acquire Land	[2]	$ 78,000

[1] Acquisition comprised of four adjacent parcels in the South Lake Union submarket of Seattle, Washington located at 330 Dexter Avenue North, 333 Dexter Avenue North, 401 Dexter Avenue North, and 400 Aurora Avenue North. In connection with this acquisition, we also assumed $2.4 million in accrued liabilities and acquisition costs that are not included in the purchase price above.

[2] In connection with this acquisition, we assumed $4.1 million in accrued liabilities and acquisition costs that are not included in the purchase price above. The Company expects to develop and own two buildings on the site encompassing office and production design and repair space totaling approximately 400,000 square feet.