Residential Whole Loans-Fair Value (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) loan	Dec. 31, 2014 USD ($) loan
Investments, Debt and Equity Securities [Abstract]
Outstanding principal balance	$ 670,068	$ 182,613
Aggregate fair value	$ 531,537	$ 143,472
Number of loans | loan	2,713	885