Loans - Summary of TDR and Related Credit Loss Reserves for TDR Loans (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
TDR Loans	$ 1,391	[1],[2],[3]	$ 1,434	[1],[2],[3]
Allowance for credit losses on TDR Loans	107	[4]	140	[4]
Unpaid Principal Balance of TDR Loans	1,620		1,701
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	490	[1],[3]	460	[1],[3]
Allowance for credit losses on TDR Loans	26	[4]	26	[4]
Unpaid Principal Balance of TDR Loans	550		569
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	435	[1],[3]	343	[1],[3]
Allowance for credit losses on TDR Loans	25	[4]	23	[4]
Unpaid Principal Balance of TDR Loans	451		398
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	27	[1],[3]	86	[1],[3]
Allowance for credit losses on TDR Loans	1	[4]	3	[4]
Unpaid Principal Balance of TDR Loans	68		137
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	28	[1],[3]	31	[1],[3]
Allowance for credit losses on TDR Loans	0	[4]	0	[4]
Unpaid Principal Balance of TDR Loans	31		34
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	901	[1],[3]	974	[1],[3]
Allowance for credit losses on TDR Loans	81	[4]	114	[4]
Unpaid Principal Balance of TDR Loans	1,070		1,132
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	890	[1],[3],[5]	960	[1],[3],[5]
Allowance for credit losses on TDR Loans	77	[4]	109	[4]
Unpaid Principal Balance of TDR Loans	1,059		1,118
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Impaired [Line Items]
TDR Loans	11	[1],[3]	14	[1],[3]
Allowance for credit losses on TDR Loans	4	[4]	5	[4]
Unpaid Principal Balance of TDR Loans	$ 11		$ 14

[1] 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:June 30, 2013 December 31, 2012 (in millions)Commercial loans: Construction and other real estate$451 $398Business and corporate banking68 137Other commercial31 34Total commercial550 569Consumer loans: Residential mortgages1,059 1,118Credit cards11 14Total consumer1,070 1,132Total$1,620 $1,701

[2] Includes balances of $404 million and $519 million at June 30, 2013 and December 31, 2012, respectively, which are classified as nonaccrual loans.

[3] 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 $125 million and $237 million at June 30, 2013 and December 31, 2012, respectively.

[4] Included in the allowance for credit losses.

[5] Includes $657 million and $608 million at June 30, 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.