Debt and Preferred Equity Investments - Preferred Equity Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Preferred equity investment
Aggregate weighted average current yield (as a percent)	9.19%
Carrying Value	$ 2,085,871	$ 2,114,041
Preferred Equity, April 2021
Preferred equity investment
Future Funding Obligations	0
Senior Financing	272,000
Carrying Value	$ 144,826	144,423
Preferred equity investments
Preferred equity investment
Aggregate weighted average current yield (as a percent)	6.97%
Future Funding Obligations	$ 0
Senior Financing	272,000
Carrying Value	$ 144,826	$ 144,423