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		6 Months Ended
	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	2,885	3,309	9,590	6,633
Amount Defaulted	$ 177	$ 184	$ 758	$ 420
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	172	216	340	457
Amount Defaulted	3	10	5	31
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	23	29	42	83
Amount Defaulted	44	72	72	164
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	187	247	370	311
Amount Defaulted	28	22	59	34
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1,638	2,390	3,624	4,916
Amount Defaulted	10	13	21	28
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	369	158	886	342
Amount Defaulted	15	1	43	4
Total Loans, Excluding GNMA and Covered Loans
Financing Receivable, Modifications [Line Items]
Number of Loans	2,389	3,040	5,262	6,109
Amount Defaulted	100	118	200	261
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	481	262	4,303	483
Amount Defaulted	68	39	546	72
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	15	7	25	41
Amount Defaulted	$ 9	$ 27	$ 12	$ 87