Loans - Trouble Debt Restructuring Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	$ 1,204	$ 1,251	$ 1,250	$ 1,305
Trouble debt restructuring interest income recognized	11	12	26	24
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	248	349	295	386
Trouble debt restructuring interest income recognized	2	4	8	7
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	220	290	244	307
Trouble debt restructuring interest income recognized	2	3	8	5
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	23	30	22	49
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	0	0	17	0
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	5	29	12	30
Trouble debt restructuring interest income recognized	0	1	0	2
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	956	902	955	919
Trouble debt restructuring interest income recognized	9	8	18	17
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	948	890	947	906
Trouble debt restructuring interest income recognized	9	8	18	17
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	$ 8	$ 12	$ 8	$ 13