Debt and Preferred Equity Investments (Preferred Equity Investments)(Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Preferred equity investment
Aggregate weighted average current yield (as a percent)	9.73%
Carrying Value	$ 1,986,413	$ 1,640,412
Preferred Equity, April 2021
Preferred equity investment
Future Funding Obligations	0
Senior Financing	272,000
Carrying Value	143,319	0
Preferred Equity redeemed in May 2017
Preferred equity investment
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	9,982
Preferred Equity redeemed in April 2017
Preferred equity investment
Future Funding Obligations	0
Senior Financing	0
Carrying Value	$ 0	37,893
Preferred equity investments
Preferred equity investment
Aggregate weighted average current yield (as a percent)	6.41%
Future Funding Obligations	$ 0
Senior Financing	272,000
Carrying Value	$ 143,319	$ 47,875