Estimated Amortization Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	$ 188
Future Amortization Expense, Year Two	203
Future Amortization Expense, Year Three	161
Future Amortization Expense, Year Four	130
Future Amortization Expense, Year Five	106
Mortgage Servicing Rights
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	179
Future Amortization Expense, Year Two	195
Future Amortization Expense, Year Three	157
Future Amortization Expense, Year Four	128
Future Amortization Expense, Year Five	104
Other Intangible Assets
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	9
Future Amortization Expense, Year Two	8
Future Amortization Expense, Year Three	4
Future Amortization Expense, Year Four	2
Future Amortization Expense, Year Five	$ 2