Residential Whole Loans - Narrative (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015 loan	Mar. 31, 2014	Dec. 31, 2014 loan
Residential Whole Loans [Abstract]
Residential whole loans	$ 387,300,000		$ 351,400,000
Equity interest in certificates (percent)	100.00%
Residential whole loans at carrying value	242,777,000		207,923,000
Residential whole loans at fair value aggregate outstanding principal balance	188,906,000		182,613,000
Residential whole loans, at fair value	144,507,000		143,472,000
Number of residential whole loans	883		885
Net income on residential whole loans held at fair value	$ 2,576,000	$ 0