Estimated Amortization Expense (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	$ 84
Future Amortization Expense, Year Two	278
Future Amortization Expense, Year Three	212
Future Amortization Expense, Year Four	165
Future Amortization Expense, Year Five	131
Mortgage Servicing Rights
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	81
Future Amortization Expense, Year Two	270
Future Amortization Expense, Year Three	208
Future Amortization Expense, Year Four	163
Future Amortization Expense, Year Five	129
Other Intangible Assets
Expected Amortization Expense [Line Items]
Future Amortization Expense, Year One	3
Future Amortization Expense, Year Two	8
Future Amortization Expense, Year Three	4
Future Amortization Expense, Year Four	2
Future Amortization Expense, Year Five	$ 2