Loans - Status of Commercial Loan Portfolio (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual Loans	$ 1,107,000,000	$ 1,305,000,000
Accruing Loans Contractually Past Due 90 days or More	30,000,000	34,000,000
Total loans	72,198,000,000	67,695,000,000	66,705,000,000
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	52,931,000,000	48,234,000,000
Nonaccrual Loans	94,000,000	254,000,000
Accruing Loans Contractually Past Due 90 days or More	8,000,000	6,000,000
Total loans	53,033,000,000	48,494,000,000
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	9,618,000,000	8,868,000,000
Nonaccrual Loans	64,000,000	166,000,000
Accruing Loans Contractually Past Due 90 days or More	0	0
Total loans	9,682,000,000	9,034,000,000	8,529,000,000
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	15,921,000,000	14,420,000,000
Nonaccrual Loans	28,000,000	21,000,000
Accruing Loans Contractually Past Due 90 days or More	7,000,000	5,000,000
Total loans	15,956,000,000	14,446,000,000	12,391,000,000
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	24,268,000,000	21,560,000,000
Nonaccrual Loans	0	65,000,000
Accruing Loans Contractually Past Due 90 days or More	0	0
Total loans	24,268,000,000	21,625,000,000	23,339,000,000
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	3,124,000,000	3,386,000,000
Nonaccrual Loans	2,000,000	2,000,000
Accruing Loans Contractually Past Due 90 days or More	1,000,000	1,000,000
Total loans	$ 3,127,000,000	$ 3,389,000,000	$ 3,005,000,000