Loans and Allowance for Credit Losses - Additional Detail of Allowance for Credit Losses and Related Loan Balances by Portfolio Type (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Allowance Balance at End of Period
Loans individually evaluated for impairment	$ 26	$ 40
TDRs collectively evaluated for impairment	703	754
Other loans collectively evaluated for impairment	3,771	3,771
Loans acquired with deteriorated credit quality	208	168
Total allowance for credit losses	4,708	4,733	4,919	5,014
Loan balance at end of period
Loans individually evaluated for impairment	691	729
TDRs collectively evaluated for impairment	5,671	5,675
Other loans collectively evaluated for impairment	212,439	211,514
Loans acquired with deteriorated credit quality	4,550	5,411
Total loans	223,351	223,329
Commercial [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	5	10
TDRs collectively evaluated for impairment	25	28
Other loans collectively evaluated for impairment	982	1,013
Total allowance for credit losses	1,012	1,051	1,029	1,010
Loan balance at end of period
Loans individually evaluated for impairment	145	171
TDRs collectively evaluated for impairment	184	185
Other loans collectively evaluated for impairment	65,991	65,863
Loans acquired with deteriorated credit quality	3	4
Total loans	66,323	66,223
Commercial Real Estate [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	21	30
TDRs collectively evaluated for impairment	25	29
Other loans collectively evaluated for impairment	741	791
Loans acquired with deteriorated credit quality	11	7
Total allowance for credit losses	798	857	1,037	1,154
Loan balance at end of period
Loans individually evaluated for impairment	484	510
TDRs collectively evaluated for impairment	400	391
Other loans collectively evaluated for impairment	36,427	35,952
Loans acquired with deteriorated credit quality	89	100
Total loans	37,400	36,953
Residential Mortgages [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	407	446
Other loans collectively evaluated for impairment	519	489
Total allowance for credit losses	926	935	927	927
Loan balance at end of period
TDRs collectively evaluated for impairment	4,282	4,199
Other loans collectively evaluated for impairment	41,696	39,813
Loans acquired with deteriorated credit quality	6	6
Total loans	45,984	44,018
Credit Card [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	132	153
Other loans collectively evaluated for impairment	763	710
Total allowance for credit losses	895	863	1,001	992
Loan balance at end of period
TDRs collectively evaluated for impairment	393	442
Other loans collectively evaluated for impairment	15,836	16,673
Total loans	16,229	17,115
Other Retail [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	110	97
Other loans collectively evaluated for impairment	744	751
Total allowance for credit losses	854	848	823	831
Loan balance at end of period
TDRs collectively evaluated for impairment	310	313
Other loans collectively evaluated for impairment	46,370	47,399
Total loans	46,680	47,712
Total loans, excluding covered loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	26	40
TDRs collectively evaluated for impairment	699	753
Other loans collectively evaluated for impairment	3,749	3,754
Loans acquired with deteriorated credit quality	11	7
Total allowance for credit losses	4,485	4,554	4,817	4,914
Loan balance at end of period
Loans individually evaluated for impairment	629	681
TDRs collectively evaluated for impairment	5,569	5,530
Other loans collectively evaluated for impairment	206,320	205,700
Loans acquired with deteriorated credit quality	98	110
Total loans	212,616	212,021
Covered Loans [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	4	1
Other loans collectively evaluated for impairment	22	17
Loans acquired with deteriorated credit quality	197	161
Total allowance for credit losses	223	179	102	100
Loan balance at end of period
Loans individually evaluated for impairment	62	48
TDRs collectively evaluated for impairment	102	145
Other loans collectively evaluated for impairment	6,119	5,814
Loans acquired with deteriorated credit quality	4,452	5,301
Total loans	$ 10,735	$ 11,308