Summary of Significant Accounting Policies - Reclassifications (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Rental income	$ 400,000
Rent and tenant receivables and other assets, net	7,844,000		$ 3,264,000
Investment in unconsolidated entities	33,736,000		39,520,000
Return of investment from unconsolidated entities	386,000	$ 408,000
Net cash provided by (used in) operating activities	(149,865,000)	(183,883,000)
Net cash (used in) provided by investing activities	108,933,000	82,001,000
Payments on mortgage notes payable and other debt, including debt extinguishment costs	$ (2,676,000)	(84,261,000)
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash (used in) provided by investing activities		(1,700,000)
Distributions Received From Equity method Investments [Member] | Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Return of investment from unconsolidated entities		400,000
Net cash (used in) provided by investing activities		400,000
Proceeds From Settlement Of Insurance Claims [Member] | Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities		44,000
Net cash (used in) provided by investing activities		44,000
Reclassification
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Direct financing lease income reclassed		$ 400,000
Investment in unconsolidated entities			$ 3,300,000