Debt and Preferred Equity Investments (Narrative)(Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) segment	Dec. 31, 2015 USD ($) segment
Preferred equity investment
Carrying Value, Net of Discounts and Deferred Origination Fees	$ 1,453,234,000	$ 1,670,020,000
Number of portfolio segments of financial receivables (segment) | segment	1	1
Additional amount of financing receivables included in other assets	$ 101,400,000	$ 121,500,000
Junior Mortgage Participation Acquired in September 2014
Preferred equity investment
Carrying Value, Net of Discounts and Deferred Origination Fees	$ 0	$ 0