Asset Quality - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Dec. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Estimated gross contractual amount receivable of PCI loans	$ 41,000,000	$ 25,000,000	$ 41,000,000	$ 25,000,000	$ 23,000,000
Estimated cash flows nonaccretable amount			11,000,000
Estimated cash flows accretable amount	5,000,000		5,000,000
Purchased Credit Impaired, Outstanding	18,000,000	25,000,000	18,000,000	25,000,000	23,000,000
Changes in the accertable yield, accretion			1,000,000
Changes in the accretable yield, net reclassifications			1,000,000
Accretable yield	5,000,000		5,000,000
Percentage of carrying amount of our commercial nonperforming loans outstanding	61.00%		61.00%
Percentage of nonperforming loans outstanding face value	74.00%		74.00%
Percentage of loans held for sale and other nonperforming assets	72.00%		72.00%
Aggregate carrying amount of largest nonperforming loans		202,000,000		202,000,000
Number of largest nonperforming loans	20	20	20	20
Total loans on nonperforming status from continuing operations	119,000,000		119,000,000
Percentage of total loans on nonperforming status	22.00%	31.00%	22.00%	31.00%
Net reduction to interest income			18,000,000		25,000,000
Interest income recognized on outstanding balances			5,000,000	4,000,000
Total restructured loans	349,000,000	323,000,000	349,000,000	323,000,000	320,000,000
Addition in restructured loans			143,000,000
Restructured loans partially in payments and charge-offs			114,000,000
Total current loan	52,700,000,000		52,700,000,000
Percent of total current loan			98.30%
Total past due loan	919,000,000	1,096,000,000	919,000,000	1,096,000,000	1,176,000,000
Percent of total past due loans	1.70%		1.70%
Minimum outstanding impaired commercial loans	2,500,000		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			180 days
Number of days to designate the charge-off policy for credit card loans taking effect, payment due period			180 days
ALLL	868,000,000	888,000,000	868,000,000	888,000,000	888,000,000
ALLL percentage			1.62%	1.73%
ALLL of nonperforming loans percentage			160.40%	136.00%
Increase (decrease) in allowance for loan losses		20,000,000
Percentage decrease in allowance for loan losses		2.00%
Individually evaluated for impairment, corresponding allowance	411,000,000	428,000,000	411,000,000	428,000,000	411,000,000
Corresponding allowance	47,000,000	39,000,000	47,000,000	39,000,000	35,000,000
Collectively Evaluated for Impairment, Outstanding	53,168,000,000	50,966,000,000	53,168,000,000	50,966,000,000	52,388,000,000
Collectively evaluated for current, corresponding allowance	820,000,000		820,000,000
Provision (credit) for loan and lease losses	28,000,000	109,000,000	111,000,000	172,000,000
Increase (decrease) liability for credit losses on lending related commitments				3,000,000
Percentage of total allowance for credit losses	1.69%	1.81%	1.69%	1.81%
Liability for credit losses on lending-related commitments	40,000,000	43,000,000	40,000,000	43,000,000	29,000,000	37,000,000	51,000,000	45,000,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased Credit Impaired, Outstanding	16,000,000	21,000,000	16,000,000	21,000,000	19,000,000
Number of loans	138		138			127
Financial receivable, modifications, subsequent default, recorded investment	7,000,000		7,000,000			5,000,000
Individually evaluated for impairment, corresponding allowance	213,000,000	156,000,000	213,000,000	156,000,000	202,000,000
Corresponding allowance	29,000,000	20,000,000	29,000,000	20,000,000	22,000,000
Collectively Evaluated for Impairment, Outstanding	15,899,000,000	15,707,000,000	15,899,000,000	15,707,000,000	15,721,000,000
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased Credit Impaired, Outstanding	25,000,000		25,000,000
Purchased credit impaired loans carrying value	18,000,000		18,000,000
Purchase Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Corresponding allowance	1,000,000		1,000,000
Collectively Evaluated for Impairment, Outstanding	18,000,000		18,000,000
Provision (credit) for loan and lease losses	$ 0