Additional Detail of Allowance for Credit Losses and Related Loan Balances by Portfolio Type (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Jun. 30, 2012	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment	$ 39	[1]		$ 80	[1]
TDRs collectively evaluated for impairment	750			839
Other loans collectively evaluated for impairment	3,888			4,016
Loans acquired with deteriorated credit quality	94			79
Total allowance for credit losses	4,771		4,864	5,014		5,190	5,308	5,531
Loan balance at end of year:
Loans individually evaluated for impairment	817	[2]		1,244	[2]
TDRs collectively evaluated for impairment	5,463			4,883
Other loans collectively evaluated for impairment	206,356			197,705
Loans acquired with deteriorated credit quality	5,514			6,003
Total loans	218,150			209,835
Commercial
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment	6	[1]		16	[1]
TDRs collectively evaluated for impairment	31			40
Other loans collectively evaluated for impairment	997			954
Total allowance for credit losses	1,034		1,037	1,010		1,025	1,109	1,104
Loan balance at end of year:
Loans individually evaluated for impairment	132	[2]		222	[2]
TDRs collectively evaluated for impairment	179			277
Other loans collectively evaluated for impairment	62,594			56,138
Loans acquired with deteriorated credit quality	5			11
Total loans	62,910			56,648
Commercial Real Estate
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment	33	[1]		61	[1]
TDRs collectively evaluated for impairment	28			33
Other loans collectively evaluated for impairment	828			1,057
Loans acquired with deteriorated credit quality	5			3
Total allowance for credit losses	894		941	1,154		1,221	1,258	1,291
Loan balance at end of year:
Loans individually evaluated for impairment	612	[2]		812	[2]
TDRs collectively evaluated for impairment	383			331
Other loans collectively evaluated for impairment	35,699			34,574
Loans acquired with deteriorated credit quality	119			134
Total loans	36,813			35,851
Residential Mortgages
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment				1	[1]
TDRs collectively evaluated for impairment	464			490
Other loans collectively evaluated for impairment	497			436
Total allowance for credit losses	961		939	927		887	841	820
Loan balance at end of year:
Loans individually evaluated for impairment				6	[2]
TDRs collectively evaluated for impairment	4,033			3,430
Other loans collectively evaluated for impairment	37,863			33,642
Loans acquired with deteriorated credit quality	6			4
Total loans	41,902			37,082
Credit Card
Allowance balance at December 31, 2011 related to
TDRs collectively evaluated for impairment	167			219
Other loans collectively evaluated for impairment	748			773
Total allowance for credit losses	915		996	992		1,068	1,140	1,395
Loan balance at end of year:
TDRs collectively evaluated for impairment	462			584
Other loans collectively evaluated for impairment	15,940			16,776
Total loans	16,402			17,360
Other Retail
Allowance balance at December 31, 2011 related to
TDRs collectively evaluated for impairment	59			57
Other loans collectively evaluated for impairment	797			774
Total allowance for credit losses	856		828	831		832	843	807
Loan balance at end of year:
TDRs collectively evaluated for impairment	269			148
Other loans collectively evaluated for impairment	47,696			47,959
Total loans	47,965			48,107
Total Loans, Excluding Covered Loans
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment	39	[1]		78	[1]
TDRs collectively evaluated for impairment	749			839
Other loans collectively evaluated for impairment	3,867			3,994
Loans acquired with deteriorated credit quality	5			3
Total allowance for credit losses	4,660		4,741	4,914		5,033	5,191	5,417
Loan balance at end of year:
Loans individually evaluated for impairment	744	[2]		1,040	[2]
TDRs collectively evaluated for impairment	5,326			4,770
Other loans collectively evaluated for impairment	199,792			189,089
Loans acquired with deteriorated credit quality	130			149
Total loans	205,992			195,048
Covered Loans
Allowance balance at December 31, 2011 related to
Loans individually evaluated for impairment				2	[1]
TDRs collectively evaluated for impairment	1
Other loans collectively evaluated for impairment	21			22
Loans acquired with deteriorated credit quality	89			76
Total allowance for credit losses	111		123	100		157	117	114
Loan balance at end of year:
Loans individually evaluated for impairment	73	[2],[3]		204	[2],[3]
TDRs collectively evaluated for impairment	137	[3]		113	[3]
Other loans collectively evaluated for impairment	6,564	[3]		8,616	[3]
Loans acquired with deteriorated credit quality	5,384	[3]		5,854	[3]
Total loans	$ 12,158	[3]		$ 14,787	[3]

[1] Represents the allowance for credit losses related to loans greater than $5 million classified as nonperforming or TDRs.

[2] Represents loans greater than $5 million classified as nonperforming or TDRs.

[3] Includes expected reimbursements from the FDIC under loss sharing agreements.