Asset Quality - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2012 SecurityLoan	Dec. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011
Estimated gross contractual amount receivable of PCI loans	$ 19,000,000		$ 19,000,000		$ 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 loans	19,000,000		19,000,000		23,000,000
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	63.00%		63.00%
Percentage of nonperforming loans outstanding face value	76.00%		76.00%
Percentage of loans held for sale and other nonperforming assets	74.00%		74.00%
Aggregate carrying amount of largest nonperforming loans	191,000,000		191,000,000
Number of largest nonperforming loans	20	20	20	20
Total loans on nonperforming status from continuing operations		220,000,000		220,000,000
Percentage of total loans on nonperforming status	29.00%	33.00%	29.00%	33.00%
Net reduction to interest income			13,000,000		25,000,000
Interest income recognized on outstanding balances	1,000,000	2,000,000
Total restructured loans	311,000,000	274,000,000	311,000,000	274,000,000	320,000,000
Addition in restructured loans			72,000,000
Restructured loans partially in payments and charge-offs			81,000,000
Total current loan	52,100,000,000		52,100,000,000
Percent of total current loan			98.10%
Total past due loan	983,000,000	1,150,000,000	983,000,000	1,150,000,000	1,176,000,000
Percent of total past due loans	1.90%		1.90%
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
ALLL	876,000,000	888,000,000	876,000,000	888,000,000	888,000,000
ALLL percentage			1.65%	1.79%
ALLL of nonperforming loans percentage			134.36%	135.16%
Increase (decrease) in allowance for loan losses	12,000,000
Percentage decrease in allowance for loan losses	1.00%
Individually evaluated for impairment, corresponding allowance	464,000,000	411,000,000	464,000,000	411,000,000	411,000,000
Corresponding allowance	34,000,000	48,000,000	34,000,000	48,000,000	35,000,000
Collectively Evaluated for Impairment, Outstanding	52,618,000,000	49,194,000,000	52,618,000,000	49,194,000,000	52,388,000,000
Collectively evaluated for current, corresponding allowance	842,000,000		842,000,000
Increase decrease liability for credit losses on lending related commitments				14,000,000
Percentage of total allowance for credit losses	1.72%	1.89%	1.72%	1.89%
Liability for credit losses on lending-related commitments	37,000,000	51,000,000	37,000,000	51,000,000	29,000,000	32,000,000	45,000,000	45,000,000
PCI Loans [Member]
Purchased credit impaired loans	27,000,000		27,000,000
Purchased credit impaired loans carrying value	19,000,000		19,000,000
Consumer Loans [Member]
Purchased credit impaired loans	17,000,000		17,000,000		19,000,000
Number of loans	127		127			240
Financial receivable, modifications, subsequent default, recorded investment	5,000,000		5,000,000			14,000,000
Individually evaluated for impairment, corresponding allowance	208,000,000	86,000,000	208,000,000	86,000,000	202,000,000
Corresponding allowance	26,000,000	18,000,000	26,000,000	18,000,000	22,000,000
Collectively Evaluated for Impairment, Outstanding	15,853,000,000	14,916,000,000	15,853,000,000	14,916,000,000	15,721,000,000
Purchase Credit Impaired Loans [Member]
Corresponding allowance	1,000,000		1,000,000
Collectively Evaluated for Impairment, Outstanding	$ 19,000,000		$ 19,000,000