Servicing Assets and Residual Interests Economic Assumptions (Detail)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Fixed Rate Residential Mortgage
Assumption For Fair Value As Of Balance Sheet Date Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities [Line Items]
Weighted- Average Life (in years)	7 years 4 months 24 days	7 years
Prepayment Speed (annual)	10.90%	10.50%
Discount Rate (annual)		9.90%
OAS spread (bps)	674
Adjustable Rate Residential Mortgage
Assumption For Fair Value As Of Balance Sheet Date Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities [Line Items]
Weighted- Average Life (in years)	2 years 9 months 18 days	3 years 8 months 12 days
Prepayment Speed (annual)	32.90%	22.20%
Discount Rate (annual)		11.80%
OAS spread (bps)	671