Equity Investments in Real Estate - Proportionate Share of Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	$ (3,906)	$ 2,780	$ 349	$ 6,532
Equity Method Investments
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(3,171)	3,882	2,611	9,940
Equity Method Investments | Net Lease
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(414)	4,056	7,016	12,369
Equity Method Investments | All Other
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(2,757)	(174)	(4,405)	(2,035)
Equity Method Investments | Self Storage
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	0	0	0	(394)
Amortization of Basis Difference on Equity Investments
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(735)	(1,102)	(2,262)	(3,408)
Amortization of Basis Difference on Equity Investments | Net Lease
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(650)	(667)	(1,775)	(2,307)
Amortization of Basis Difference on Equity Investments | All Other
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	(85)	(435)	(487)	(1,062)
Amortization of Basis Difference on Equity Investments | Self Storage
Equity Method Investment, Financial Statement, Reported Amounts
Equity in (losses) earnings of equity method investments in real estate	$ 0	$ 0	$ 0	$ (39)