Loans - Impaired Commercial Loans Considered as TDR Loans (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2012	Jun. 30, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired commercial loans as TDR		$ 1,391	[1],[2],[3]	$ 1,434	[1],[2],[3]
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial loans as TDR		490	[1],[3]	460	[1],[3]
Unpaid principal balance of impaired commercial loans		675		806
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Charge-off of impaired loan	57
Impaired commercial loans as TDR		435	[1],[3]	343	[1],[3]
Unpaid principal balance of impaired commercial loans		481		552
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial loans as TDR		27	[1],[3]	86	[1],[3]
Unpaid principal balance of impaired commercial loans		109		157
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance of impaired commercial loans		18		18
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial loans as TDR		28	[1],[3]	31	[1],[3]
Unpaid principal balance of impaired commercial loans		$ 67		$ 79

[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.