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	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for loan losses
Loans collectively evaluated for impairment	$ 8,437	$ 13,058
Loans collectively evaluated for impairment and acquired with deteriorated credit quality	1,596	1,262
Total	10,033	14,320	20,435	13,824
Recorded investment in residential loans at amortized cost
Loans collectively evaluated for impairment	1,299,514	1,383,252
Loans collectively evaluated for impairment and acquired with deteriorated credit quality	25,058	25,939
Total	$ 1,324,572	$ 1,409,191