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	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Allowance Balance at End of Period
Loans individually evaluated for impairment	$ 16		$ 40
TDRs collectively evaluated for impairment	572		754
Other loans collectively evaluated for impairment	3,828		3,771
Loans acquired with deteriorated credit quality	162		168
Total allowance for credit losses	4,578	4,612	4,733	4,771	4,864	5,014
Loan balance at end of period
Loans individually evaluated for impairment	472		729
TDRs collectively evaluated for impairment	5,604		5,675
Other loans collectively evaluated for impairment	221,139		211,514
Loans acquired with deteriorated credit quality	4,164		5,411
Total Loans	221,983		212,021
Total loans	231,379		223,329
Commercial [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	9		10
TDRs collectively evaluated for impairment	21		28
Other loans collectively evaluated for impairment	1,001		1,013
Loans acquired with deteriorated credit quality
Total allowance for credit losses	1,031	1,023	1,051	1,034	1,037	1,010
Loan balance at end of period
Loans individually evaluated for impairment	171		171
TDRs collectively evaluated for impairment	171		185
Other loans collectively evaluated for impairment	68,615		65,863
Loans acquired with deteriorated credit quality	1		4
Total Loans	68,958		66,223
Commercial Real Estate [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	7		30
TDRs collectively evaluated for impairment	21		29
Other loans collectively evaluated for impairment	719		791
Loans acquired with deteriorated credit quality	14		7
Total allowance for credit losses	761	777	857	894	941	1,154
Loan balance at end of period
Loans individually evaluated for impairment	253		510
TDRs collectively evaluated for impairment	360		391
Other loans collectively evaluated for impairment	37,979		35,952
Loans acquired with deteriorated credit quality	86		100
Total Loans	38,678		36,953
Residential Mortgages [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	341		446
Other loans collectively evaluated for impairment	593		489
Loans acquired with deteriorated credit quality
Total allowance for credit losses	934	921	935	961	939	927
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	4,357		4,199
Other loans collectively evaluated for impairment	45,812		39,813
Loans acquired with deteriorated credit quality	1		6
Total Loans	50,170		44,018
Credit Card [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	101		153
Other loans collectively evaluated for impairment	764		710
Loans acquired with deteriorated credit quality
Total allowance for credit losses	865	874	863	915	996	992
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	335		442
Other loans collectively evaluated for impairment	16,728		16,673
Loans acquired with deteriorated credit quality
Total Loans	17,063		17,115
Other Retail [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	83		97
Other loans collectively evaluated for impairment	741		751
Loans acquired with deteriorated credit quality
Total allowance for credit losses	824	838	848	856	828	831
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	281		313
Other loans collectively evaluated for impairment	46,833		47,399
Loans acquired with deteriorated credit quality
Total Loans	47,114		47,712
Total Loans, Excluding Covered Loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	16		40
TDRs collectively evaluated for impairment	567		753
Other loans collectively evaluated for impairment	3,818		3,754
Loans acquired with deteriorated credit quality	14		7
Total allowance for credit losses	4,415	4,433	4,554	4,660	4,741	4,914
Loan balance at end of period
Loans individually evaluated for impairment	424		681
TDRs collectively evaluated for impairment	5,504		5,530
Other loans collectively evaluated for impairment	215,967		205,700
Loans acquired with deteriorated credit quality	88		110
Total Loans	221,983		212,021
Covered Loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	5		1
Other loans collectively evaluated for impairment	10		17
Loans acquired with deteriorated credit quality	148		161
Total allowance for credit losses	163	179	179	111	123	100
Loan balance at end of period
Loans individually evaluated for impairment	48		48
TDRs collectively evaluated for impairment	100		145
Other loans collectively evaluated for impairment	5,172		5,814
Loans acquired with deteriorated credit quality	4,076		5,301
Total loans	$ 9,396		$ 11,308