Servicing Assets and Residual Interests Economic Assumptions (Detail)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Fixed Rate Residential Mortgage
Servicing Assets at Amortized Value
Weighted- Average Life (in years)	7 years 4 months 24 days	6 years 10 months 24 days
Prepayment Speed (annual)	8.90%	9.10%
Discount Rate (annual)	10.30%	10.40%
Adjustable Rate Residential Mortgage
Servicing Assets at Amortized Value
Weighted- Average Life (in years)	3 years 8 months 12 days	3 years 8 months 12 days
Prepayment Speed (annual)	22.50%	22.20%
Discount Rate (annual)	11.50%	11.40%