Loans - Credit Risk Profile of Commercial Loans (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 67,695		$ 63,258		$ 51,867
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	48,494		44,150
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,034		8,457		7,860
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,446		12,608		10,225
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	21,625		20,009		12,658
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,389		3,076		2,906
Commercial Loan [Member] | External Credit Rating, Investment Grade [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	33,567	[1]	28,198	[1]
Commercial Loan [Member] | External Credit Rating, Investment Grade [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,069	[1]	4,727	[1]
Commercial Loan [Member] | External Credit Rating, Investment Grade [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,279	[1]	6,012	[1]
Commercial Loan [Member] | External Credit Rating, Investment Grade [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	18,636	[1]	16,206	[1]
Commercial Loan [Member] | External Credit Rating, Investment Grade [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,583	[1]	1,253	[1]
Commercial Loan [Member] | External Credit Rating, Non Investment Grade [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,927		15,952
Commercial Loan [Member] | External Credit Rating, Non Investment Grade [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,965		3,730
Commercial Loan [Member] | External Credit Rating, Non Investment Grade [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,167		6,596
Commercial Loan [Member] | External Credit Rating, Non Investment Grade [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,989		3,803
Commercial Loan [Member] | External Credit Rating, Non Investment Grade [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 1,806		$ 1,823

[1] Investment grade includes commercial loans with credit ratings of at least BBB- or above or the equivalent based on our internal credit rating system.