Loans - Status of Commercial Loan Portfolio (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual Loans	$ 1,175,000,000	$ 1,305,000,000
Accruing Loans Contractually Past Due 90 days or More	34,000,000	34,000,000
Total loans	68,897,000,000	67,695,000,000	62,932,000,000
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	49,768,000,000	48,234,000,000
Nonaccrual Loans	118,000,000	254,000,000
Accruing Loans Contractually Past Due 90 days or More	7,000,000	6,000,000
Total loans	49,893,000,000	48,494,000,000
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	9,071,000,000	8,868,000,000
Nonaccrual Loans	94,000,000	166,000,000
Accruing Loans Contractually Past Due 90 days or More	0	0
Total loans	9,165,000,000	9,034,000,000	8,319,000,000
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	15,671,000,000	14,420,000,000
Nonaccrual Loans	21,000,000	21,000,000
Accruing Loans Contractually Past Due 90 days or More	6,000,000	5,000,000
Total loans	15,698,000,000	14,446,000,000	12,725,000,000
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	21,979,000,000	21,560,000,000
Nonaccrual Loans	0	65,000,000
Accruing Loans Contractually Past Due 90 days or More	0	0
Total loans	21,979,000,000	21,625,000,000	19,718,000,000
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	3,047,000,000	3,386,000,000
Nonaccrual Loans	3,000,000	2,000,000
Accruing Loans Contractually Past Due 90 days or More	1,000,000	1,000,000
Total loans	$ 3,051,000,000	$ 3,389,000,000	$ 2,877,000,000