Servicing Assets and Residual Interests Economic Assumptions (Detail)	Sep. 30, 2011 years	Sep. 30, 2010 years
Fixed Rate Residential Mortgage
Servicing Assets at Amortized Value [Line Items]
Weighted- Average Life (in years)	6.3	6.0
Prepayment Speed (annual)	11.10%	12.70%
Discount Rate (annual)	10.50%	10.70%
Adjustable Rate Residential Mortgage
Servicing Assets at Amortized Value [Line Items]
Weighted- Average Life (in years)	3.7	3.4
Prepayment Speed (annual)	22.30%	24.40%
Discount Rate (annual)	11.40%	11.60%