Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012
Fair Value, Inputs, Level 3 | Residential mortgage loans | Fair value, recurring
Quantitative information about level 3 fair value measurements
Residential mortgage loans	$ 76
Fair Value, Inputs, Level 3 | IRLCs, net | Fair value, recurring
Quantitative information about level 3 fair value measurements
Derivative instruments	54
Fair Value, Inputs, Level 3 | Stock warrants associated with the sale of the processing business | Fair value, recurring
Quantitative information about level 3 fair value measurements
Derivative instruments	213
Fair Value, Inputs, Level 3 | Swap associated with the sale of Visa, Inc. Class B shares | Fair value, recurring
Quantitative information about level 3 fair value measurements
Derivative instruments	(29)
Fair Value, Inputs, Level 3 | Commercial Loans Held For Sale | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Fair value measurements nonrecurring assets	8
Fair Value, Inputs, Level 3 | OREO Property | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Fair value measurements nonrecurring assets	134
Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Fair value measurements nonrecurring assets	77
Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Default rates	100.00%
Fair value measurements nonrecurring assets	95
Fair Value, Inputs, Level 3 | Commercial Construction Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Default rates	100.00%
Fair value measurements nonrecurring assets	26
Fair Value, Inputs, Level 3 | Mortgage Servicing Rights | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Fair value measurements nonrecurring assets	$ 736
Minimum | Stock warrants associated with the sale of the processing business | Fair value, recurring
Quantitative information about level 3 fair value measurements
Risk free rate	0.30%
Minimum | Fair Value, Inputs, Level 3 | Residential mortgage loans | Fair value, recurring
Quantitative information about level 3 fair value measurements
Interest rate risk factor	(90.80%)
Credit risk factor	2.20%
Minimum | Fair Value, Inputs, Level 3 | IRLCs, net | Fair value, recurring
Quantitative information about level 3 fair value measurements
Loan closing rates	9.90%
Minimum | Fair Value, Inputs, Level 3 | Stock warrants associated with the sale of the processing business | Fair value, recurring
Quantitative information about level 3 fair value measurements
Expected term (years)	1.75
Expected volatility	29.00%	[1]
Minimum | Fair Value, Inputs, Level 3 | Swap associated with the sale of Visa, Inc. Class B shares | Fair value, recurring
Quantitative information about level 3 fair value measurements
Timing of the resolution of the covered litigation	6/30/2013
Minimum | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	0.00%
Minimum | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	0.00%
Minimum | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	0.00%
Minimum | Fair Value, Inputs, Level 3 | Mortgage Servicing Rights | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Prepayment speed	0.00%
Discount rate	9.40%
Maximum | Fair Value, Inputs, Level 3 | Residential mortgage loans | Fair value, recurring
Quantitative information about level 3 fair value measurements
Interest rate risk factor	16.50%
Credit risk factor	68.40%
Maximum | Fair Value, Inputs, Level 3 | IRLCs, net | Fair value, recurring
Quantitative information about level 3 fair value measurements
Loan closing rates	86.90%
Maximum | Fair Value, Inputs, Level 3 | Stock warrants associated with the sale of the processing business | Fair value, recurring
Quantitative information about level 3 fair value measurements
Expected term (years)	17.0
Expected volatility	41.20%	[1]
Risk free rate	2.60%
Maximum | Fair Value, Inputs, Level 3 | Swap associated with the sale of Visa, Inc. Class B shares | Fair value, recurring
Quantitative information about level 3 fair value measurements
Timing of the resolution of the covered litigation	6/30/2015
Maximum | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Default rates	100.00%
Loss severities	100.00%
Maximum | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	100.00%
Maximum | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	62.80%
Maximum | Fair Value, Inputs, Level 3 | Mortgage Servicing Rights | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Prepayment speed	100.00%
Discount rate	18.00%
Weighted average | Fair Value, Inputs, Level 3 | Residential mortgage loans | Fair value, recurring
Quantitative information about level 3 fair value measurements
Interest rate risk factor	5.50%
Credit risk factor	4.40%
Weighted average | Fair Value, Inputs, Level 3 | IRLCs, net | Fair value, recurring
Quantitative information about level 3 fair value measurements
Loan closing rates	54.00%
Weighted average | Fair Value, Inputs, Level 3 | Stock warrants associated with the sale of the processing business | Fair value, recurring
Quantitative information about level 3 fair value measurements
Expected term (years)	4.8
Expected volatility	35.40%	[1]
Risk free rate	0.80%
Weighted average | Fair Value, Inputs, Level 3 | Commercial Loans Held For Sale | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Cost to sell	10.00%
Weighted average | Fair Value, Inputs, Level 3 | OREO Property | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Cost to sell	10.00%
Weighted average | Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	15.70%
Weighted average | Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	9.40%
Weighted average | Fair Value, Inputs, Level 3 | Commercial Construction Loans | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Loss severities	3.60%
Fixed | Fair Value, Inputs, Level 3 | Mortgage Servicing Rights | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Prepayment speed	15.20%
Discount rate	10.60%
Adjustable | Fair Value, Inputs, Level 3 | Mortgage Servicing Rights | Fair value, nonrecurring
Quantitative information about level 3 fair value measurements
Prepayment speed	27.10%
Discount rate	11.70%

[1] Based on historical and implied volatilities of comparable companies assuming similar expected terms.