Loans and Allowance for Credit Losses - Loans Modified as TDRs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 SecurityLoan	Mar. 31, 2013 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	11,341	12,674
Pre-Modification Outstanding Loan Balance	$ 487	$ 551
Post-Modification Outstanding Loan Balance	469	536
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	619	815
Pre-Modification Outstanding Loan Balance	79	34
Post-Modification Outstanding Loan Balance	77	33
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	15	63
Pre-Modification Outstanding Loan Balance	11	80
Post-Modification Outstanding Loan Balance	8	78
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	528	807
Pre-Modification Outstanding Loan Balance	70	110
Post-Modification Outstanding Loan Balance	70	105
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6,816	7,818
Pre-Modification Outstanding Loan Balance	40	48
Post-Modification Outstanding Loan Balance	40	48
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	787	1,865
Pre-Modification Outstanding Loan Balance	21	49
Post-Modification Outstanding Loan Balance	20	49
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	8,765	11,368
Pre-Modification Outstanding Loan Balance	221	321
Post-Modification Outstanding Loan Balance	215	313
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,563	1,256
Pre-Modification Outstanding Loan Balance	257	177
Post-Modification Outstanding Loan Balance	246	182
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	13	50
Pre-Modification Outstanding Loan Balance	9	53
Post-Modification Outstanding Loan Balance	$ 8	$ 41