Loans - Summary of TDR and Related Credit Loss Reserves for TDR Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
TDR Loans	$ 1,243	[1],[2],[3]	$ 1,434	[1],[2],[3]
Allowance for credit losses on TDR Loans	108	[4]	140	[4]
Unpaid Principal Balance of TDR Loans	1,466		1,701
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	361	[1],[3]	460	[1],[3]
Allowance for credit losses on TDR Loans	23	[4]	26	[4]
Unpaid Principal Balance of TDR Loans	424		569
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	297	[1],[3]	343	[1],[3]
Allowance for credit losses on TDR Loans	21	[4]	23	[4]
Unpaid Principal Balance of TDR Loans	318		398
Commercial Loan [Member] | Business Banking and Middle Markets Enterprises [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	34	[1],[3]	86	[1],[3]
Allowance for credit losses on TDR Loans	2	[4]	3	[4]
Unpaid Principal Balance of TDR Loans	73		137
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	30	[1],[3]	31	[1],[3]
Allowance for credit losses on TDR Loans	0	[4]	0	[4]
Unpaid Principal Balance of TDR Loans	33		34
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	882	[1],[3]	974	[1],[3]
Allowance for credit losses on TDR Loans	85	[4]	114	[4]
Unpaid Principal Balance of TDR Loans	1,042		1,132
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	869	[1],[3],[5]	960	[1],[3],[5]
Allowance for credit losses on TDR Loans	80	[4]	109	[4]
Unpaid Principal Balance of TDR Loans	1,029		1,118
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	13	[1],[3]	14	[1],[3]
Allowance for credit losses on TDR Loans	5	[4]	5	[4]
Unpaid Principal Balance of TDR Loans	$ 13		$ 14

[1] TDR Loans are considered to be impaired loans. For consumer loans, all such loans are considered impaired loans regardless of accrual status. For commercial loans, impaired loans include other loans in addition to TDRs which totaled $171 million and $237 million at March 31, 2013 and December 31, 2012, respectively.

[2] Includes balances of $416 million and $519 million at March 31, 2013 and December 31, 2012, respectively, which are classified as nonaccrual loans.

[3] The TDR Loan balances included in the table above reflect the current carrying amount of TDR Loans and includes all basis adjustments on the loan, such as unearned income, unamortized deferred fees and costs on originated loans, partial charge-offs and premiums or discounts on purchased loans. The following table reflects the unpaid principal balance of TDR Loans:March 31, 2013 December 31, 2012 (in millions)Commercial loans: Construction and other real estate$318 $398Business and corporate banking73 137Other commercial33 34Total commercial424 569Consumer loans: Residential mortgages1,029 1,118Credit cards13 14Total consumer1,042 1,132Total$1,466 $1,701

[4] Included in the allowance for credit losses.

[5] Includes $632 million and $445 million at March 31, 2013 and December 31, 2012, respectively, of loans that are recorded at the lower of amortized cost or fair value of the collateral less cost to sell.