Estimated Amortization Expense (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Expected Amortization Expense
Future Amortization Expense, Year One	$ 31
Future Amortization Expense, Year Two	115
Future Amortization Expense, Year Three	103
Future Amortization Expense, Year Four	94
Future Amortization Expense, Year Five	87
Servicing Rights
Expected Amortization Expense
Future Amortization Expense, Year One	29
Future Amortization Expense, Year Two	110
Future Amortization Expense, Year Three	101
Future Amortization Expense, Year Four	92
Future Amortization Expense, Year Five	85
Other Intangible Assets
Expected Amortization Expense
Future Amortization Expense, Year One	2
Future Amortization Expense, Year Two	5
Future Amortization Expense, Year Three	2
Future Amortization Expense, Year Four	2
Future Amortization Expense, Year Five	$ 2