Asset Quality - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2012 SecurityLoan	Sep. 30, 2011 SecurityLoan	Dec. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2010
Estimated gross contractual amount receivable of PCI loans	$ 41
Estimated cash flows nonaccretable amount	11,000,000
Estimated cash flows accretable amount	5,000,000
Percentage of carrying amount of our commercial nonperforming loans outstanding	59.00%
Percentage of nonperforming loans outstanding face value	70.00%
Percentage of loans held for sale and other nonperforming assets	67.00%
Aggregate carrying amount of largest nonperforming loans	202,000,000
Number of largest nonperforming loans	20	20
Total loans on nonperforming status from continuing operations		265,000,000
Percentage of total loans on nonperforming status	31.00%	34.00%
Net reduction to interest income	18,000,000		31,000,000
Interest income recognized on outstanding balances	4,000,000	4,000,000
Total Restructured loans	323,000,000	277,000,000	276,000,000
Addition in restructured loans	192,000,000
Restructured loans partially in payments and charge-offs	144,000,000
Trial period HAMP loans included in TDR amounts	3,000,000
Secured loans discharged	38,000,000
Total current loan	50,298,000,000	46,811,000,000
Percent of total current loan	98.00%
Total Past Due Loan	1,096,000,000	1,384,000,000
Percent of total past due loans	2.00%
Purchased credit impaired loans	25,000,000
Minimum outstanding impaired commercial loans	2,500,000
Number of days to designate commercial loans will be charged off in full or charged down to the fair value of the underlying collateral payment due period	180 days
Number of days to designate the charge-off policy for most consumer loans taking effect, payment due period	120 days
Number of days to designate home equity and residential mortgage loans to get charged down to the fair value of the underlying collateral payment due period
ALLL	888,000,000	1,131,000,000	1,004,000,000
ALLL percentage	1.73%	2.35%
ALLL of non performing loans percentage	135.99%	143.53%
Increase (decrease) in allowance for loan losses	243,000,000
Percentage decrease in allowance for loan losses	21.00%
Individually Evaluated for Impairment corresponding allowance	428,000,000	441,000,000
Individually Evaluated for Impairment Allowance	39,000,000	44,000,000
Collectively Evaluated for Impairment, Outstanding	50,966,000,000	47,754,000,000
Collectively evaluated for current corresponding allowance	849,000,000
Increase (decrease) in liability for credit losses on lending-related commitments		13,000,000
Liability for credit losses on lending-related commitments	43,000,000	56,000,000	45,000,000	51,000,000	57,000,000	73,000,000
Percentage of total allowance for credit losses	1.81%	2.46%
Purchase Credit Impaired Loans [Member]
Collectively Evaluated for Impairment, Outstanding	25,000,000
Secured Loans at Banks [Member]
Secured loans discharged	$ 38,000,000