Loans - Impaired Commercial Loans Considered as TDR Loans (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2013	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired commercial loans as TDR		$ 1,435	[1],[2],[3]	$ 1,434	[1],[2],[3]
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		175		250
Performing loans added during the period	152
Impaired commercial loans as TDR		504	[1],[2]	460	[1],[2]
Unpaid principal balance of impaired commercial loans		661		806
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		71		192
Impaired commercial loans as TDR		375	[1],[2]	343	[1],[2]
Unpaid principal balance of impaired commercial loans		438		552
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		39		57
Impaired commercial loans as TDR		51	[1],[2]	86	[1],[2]
Unpaid principal balance of impaired commercial loans		94		157
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		65		0
Impaired commercial loans as TDR		51	[1],[2]	0	[1],[2]
Unpaid principal balance of impaired commercial loans		65		18
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amount with Impairment Reserves		0		1
Impaired commercial loans as TDR		27	[1],[2]	31	[1],[2]
Unpaid principal balance of impaired commercial loans		$ 64		$ 79

[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 $98 million and $237 million at September 30, 2013 and December 31, 2012, respectively.

[2] 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: September 30, 2013 December 31, 2012 (in millions)Commercial loans: Construction and other real estate$393 $398Business and corporate banking89 137Global banking51 —Other commercial30 34Total commercial563 569Consumer loans: Residential mortgages1,101 1,118Credit cards10 14Total consumer1,111 1,132Total$1,674 $1,701

[3] Includes $404 million and $519 million at September 30, 2013 and December 31, 2012, respectively, which are classified as nonaccrual loans.