Loans - Average Balance and Interest Income Recognized on Impaired Commercial Loans (Detail) (Commercial Loan [Member], 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, Impaired [Line Items]
Total average balance of impaired commercial loans	$ 288	$ 498	$ 352	$ 564
Total interest income recognized on impaired commercial loans	2	6	8	10
Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Total average balance of impaired commercial loans	237	353	269	401
Total interest income recognized on impaired commercial loans	2	4	8	7
Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Total average balance of impaired commercial loans	36	58	37	74
Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Total average balance of impaired commercial loans	0	18	22	18
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total average balance of impaired commercial loans	15	69	24	71
Total interest income recognized on impaired commercial loans	$ 0	$ 2	$ 0	$ 3