Residential Whole Loans-Fair Value (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) loan	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) loan
Investments, Debt and Equity Securities [Abstract]
Outstanding principal balance	$ 247,310		$ 247,310		$ 182,613
Aggregate fair value	183,861		$ 183,861		$ 143,472
Number of loans | loan			1,042		885
Net gain on residential whole loans held at fair value	$ 3,163	$ 0	$ 5,197	$ 0