Loans - Summary of Past Due Status of Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	$ 461		$ 588
Days Past Due, 90 + days	1,135		1,229
Total Past Due	1,596		1,817
Current	67,301	[1]	65,878	[1]
Total loans	68,897		67,695		62,932
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	51		89
Days Past Due, 90 + days	60		106
Total Past Due	111		195
Current	49,782	[1]	48,299	[1]
Total loans	49,893		48,494
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	8		6
Days Past Due, 90 + days	30		58
Total Past Due	38		64
Current	9,127	[1]	8,970	[1]
Total loans	9,165		9,034		8,319
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	17		48
Days Past Due, 90 + days	27		36
Total Past Due	44		84
Current	15,654	[1]	14,362	[1]
Total loans	15,698		14,446		12,725
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	0		8
Days Past Due, 90 + days	3		3
Total Past Due	3		11
Current	21,976	[1]	21,614	[1]
Total loans	21,979		21,625		19,718
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	26		27
Days Past Due, 90 + days	0		9
Total Past Due	26		36
Current	3,025	[1]	3,353	[1]
Total loans	3,051		3,389		2,877
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	410		499
Days Past Due, 90 + days	1,075		1,123
Total Past Due	1,485		1,622
Current	17,519	[1]	17,579	[1]
Total loans	19,004		19,201
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	366		443
Days Past Due, 90 + days	996		1,037
Total Past Due	1,362		1,480
Current	14,538	[1]	14,346	[1]
Total loans	15,900		15,826		15,730
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	22		28
Days Past Due, 90 + days	53		59
Total Past Due	75		87
Current	1,863	[1]	1,924	[1]
Total loans	1,938		2,011		2,236
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	12		16
Days Past Due, 90 + days	14		14
Total Past Due	26		30
Current	657	[1]	824	[1]
Total loans	683		854		749
Consumer Loans [Member] | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days Past Due, 30-89 days	10		12
Days Past Due, 90 + days	12		13
Total Past Due	22		25
Current	461	[1]	485	[1]
Total loans	$ 483		$ 510		$ 578

[1] Loans less than 30 days past due are presented as current.