Loans - Summary of Criticized Assets for Commercial Loans (Detail) (Commercial Loan [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	$ 2,038	$ 2,158
Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	727	1,409
Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	715	494
Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	484	143
Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	112	112
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	1,354	1,125
Special Mention [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	351	627
Special Mention [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	557	369
Special Mention [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	367	93
Special Mention [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	79	36
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	647	916
Substandard [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	346	677
Substandard [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	156	115
Substandard [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	112	50
Substandard [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	33	74
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	37	117
Doubtful [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	30	105
Doubtful [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	2	10
Doubtful [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	5	0
Doubtful [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases doubtful receivable commercial net of deferred income	$ 0	$ 2