Estimated Amortization Expense (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Expected Amortization Expense [Line Items]
Next twelve months	$ 292
Year two	224
Year three	175
Year four	139
Year five	111
Mortgage Servicing Rights
Expected Amortization Expense [Line Items]
Next twelve months	284
Year two	220
Year three	173
Year four	137
Year five	109
Other Intangible Assets
Expected Amortization Expense [Line Items]
Next twelve months	8
Year two	4
Year three	2
Year four	2
Year five	$ 2