Residential Loans at Amortized Cost, Net - Schedule of Activity in Allowance for Loan Losses on Residential Loans at Amortized Cost, Net (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Apr. 27, 2015 Trust
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of the year	$ 4,457	$ 10,033	$ 14,320
Provision for loan losses	2,701	3,142	1,491
Charge-offs, net of recoveries	(1,991)	(3,034)	(5,778)
Sale of residual interests	0	(5,684)	0
Balance at end of the year	5,167	4,457	10,033
Charge-offs recognized upon acquisition of real estate in satisfaction of residential loans	$ 1,400	$ 1,700	$ 4,300
Variable Interest Entity, Primary Beneficiary [Member] | Residual Trusts [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Number of Residual Trusts sold | Trust				7