Real Estate Joint Ventures - Summarized Financial Information for Unconsolidated Investments (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Investments in and Advances to Affiliates [Line Items]
Total assets	$ 919,686						$ 919,686		$ 1,027,945
Equity	550,722						550,722		669,293
Net loss	$ (6,141)		$ (2,696)				$ (20,943)	$ (12,830)
Other affiliates
Investments in and Advances to Affiliates [Line Items]
Total assets		$ 10,800			$ 10,800				11,500
Accounts payable and other liabilities		300			300				600
Equity		10,500			10,500				$ 10,900
Net loss		$ 200		$ 200	$ 400	$ 500