Residential Loans at Amortized Cost, Net - Schedule of Ending Balance of Allowance for Loan Losses and Recorded Investment in Residential Loans Carried at Amortized Cost by Basis of Accounting (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Allowance for loan losses
Loans collectively evaluated for impairment	$ 8,589	$ 8,437
Loans collectively evaluated for impairment and acquired with deteriorated credit quality	2,071	1,596
Total	10,660	10,033	12,084	14,320
Recorded investment in residential loans at amortized cost
Loans collectively evaluated for impairment	1,274,488	1,299,514
Loans collectively evaluated for impairment and acquired with deteriorated credit quality	25,070	25,058
Total	$ 1,299,558	$ 1,324,572