Debt and Preferred Equity Investments (Details 3) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) segment	Dec. 31, 2014 USD ($) segment
Investments, Debt and Equity Securities [Abstract]
Number of portfolio segments of financial receivables (segment) | segment	1	1
Additional amount of financing receivables included in other assets	$ 115.5	$ 133.5