Summary of Significant Accounting Policies - Properties in Development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2016
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs	$ 522,490
Other Cost and Expense, Operating	1,500	$ 1,700	$ 2,300
Impairment of Real Estate	1,700
Impairment Losses Related to Real Estate Partnerships	(1,300)	(1,300)
Refundable deposits - development
Property, Plant and Equipment [Line Items]
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs	$ 1,200	$ 1,300