Other Noninterest Income and Other Noninterest Expense Summary of Other Noninterest Expense (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
	May 02, 2011
5.70% Senior Notes
Other Noninterest Expense [Line Items]
Repurchases of principal amount of 5.70% Senior Notes and 6.05% Subordinated Notes	$ 109
6.05% Subordinated Notes
Other Noninterest Expense [Line Items]
Repurchases of principal amount of 5.70% Senior Notes and 6.05% Subordinated Notes	$ 204