Loans - Additional Information (Detail) (USD $)									9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Consumer Banking Performing	Dec. 31, 2013 Consumer Banking Performing	Sep. 30, 2014 Commercial Banking Performing	Dec. 31, 2013 Commercial Banking Performing	Sep. 30, 2014 Commercial Banking	Dec. 31, 2013 Commercial Banking	Sep. 30, 2014 Commercial Banking Criticized	Sep. 30, 2014 Commercial Banking Noncriticized	Sep. 30, 2014 Credit Card	Dec. 31, 2013 Credit Card	Sep. 30, 2014 Other Portfolio Segments, Excluding Credit Card	Dec. 31, 2013 Other Portfolio Segments, Excluding Credit Card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans accounted for based on expected cash flows	$ 24,685,000,000	$ 28,550,000,000					$ 210,000,000	$ 262,000,000			$ 28,000,000	$ 63,000,000
Loans held for sale	427,000,000	218,000,000
Minimum loan amount reviewed quarterly by management for further deterioration									1,000,000
Minimum loan amount requiring annual review										1,000,000
Troubled debt restructurings included in impaired loans	1,600,000,000	1,700,000,000	995,000,000	1,100,000,000	204,000,000	180,000,000
Unused credit card lines available to customers											$ 289,100,000,000	$ 276,700,000,000	$ 23,500,000,000	$ 20,900,000,000