Equity Investments in Real Estate - Proportionate Share of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	$ 11,145	$ 2,270	$ 15,828	$ 4,255
Equity Method Investments
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	11,747	2,935	17,042	5,782
Equity Method Investments | Net Lease
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	11,745	2,475	16,447	7,430
Equity Method Investments | All Other
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	2	460	595	(1,648)
Amortization of Basis Difference on Equity Investments
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	(602)	(665)	(1,214)	(1,527)
Amortization of Basis Difference on Equity Investments | Net Lease
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	(525)	(562)	(1,060)	(1,125)
Amortization of Basis Difference on Equity Investments | All Other
Equity Method Investment, Financial Statement, Reported Amounts
Equity in earnings of equity method investments in real estate	$ (77)	$ (103)	$ (154)	$ (402)