Valuation Assumption Ranges for Derivative Commitments (Detail)	Sep. 30, 2012 BasisPoint
Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected loan close rate	9.00%
Inherent MSR value (basis points per loan)	10
Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected loan close rate	100.00%
Inherent MSR value (basis points per loan)	195
Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected loan close rate	73.00%
Inherent MSR value (basis points per loan)	99