Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs in the Past Twelve Months that have Subsequently Defaulted (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2014 SecurityLoan	Sep. 30, 2013 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	2,493	2,755	6,527	12,345
Amount Defaulted	$ 112	$ 208	$ 221	$ 966
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	161	143	456	483
Amount Defaulted	34	37	42	42
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	4	30	16	72
Amount Defaulted		18	10	90
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	147	303	424	673
Amount Defaulted	22	41	61	100
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1,665	1,485	4,586	5,109
Amount Defaulted	9	8	25	29
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	146	278	489	1,164
Amount Defaulted	5	10	15	53
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,123	2,239	5,971	7,501
Amount Defaulted	70	114	153	314
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	366	492	542	4,795
Amount Defaulted	41	69	63	615
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	4	24	14	49
Amount Defaulted	$ 1	$ 25	$ 5	$ 37