Servicing of Residential Loans - Schedule of Fair Value Assumptions, Fair Value of Servicing Rights on Date of Sale (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Transfers and Servicing [Abstract]
Weighted-average life in years	6 years 2 months 12 days	6 years 2 months 12 days	6 years 4 months 24 days	6 years 2 months 12 days
Weighted-average discount rate	14.62%	12.20%	14.02%	12.72%
Weighted-average conditional prepayment rate	9.79%	9.11%	8.72%	9.41%
Weighted-average conditional default rate	0.53%	0.46%	0.44%	0.38%