Loans and Allowance for Credit Losses - Schedule of Loans Modified as TDRs that have Subsequently been Fully or Partially Charged-Off or Became 90 Days or More Past Due (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	2,755	3,305	12,345	9,938
Amount Defaulted	$ 208	$ 99	$ 966	$ 519
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	143	195	483	652
Amount Defaulted	37	2	42	33
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	30	13	72	96
Amount Defaulted	18	12	90	176
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	303	116	673	427
Amount Defaulted	41	30	100	64
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1,485	2,536	5,109	7,452
Amount Defaulted	8	14	29	42
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	278	189	1,164	531
Amount Defaulted	10	4	53	8
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,239	3,049	7,501	9,158
Amount Defaulted	114	62	314	323
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	492	248	4,795	731
Amount Defaulted	69	34	615	106
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	24	8	49	49
Amount Defaulted	$ 25	$ 3	$ 37	$ 90