Loans and asset quality- Allowance for Credit Losses Activity (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 57,527	[1]		$ 51,657	[1]
Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	42,098			38,230
Overdrafts
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	6,301			3,715
Overdrafts | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	1,235		1,748	1,314		1,487
Margin loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	17,548			15,652
Margin loans | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	17,548		17,685	15,652		15,146
Other | Domestic
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 855		$ 842	$ 768		$ 701

[1] Net of unearned income of $894 million at Sept. 30, 2014 and $1,020 million at Dec. 31, 2013 primarily on domestic and foreign lease financings.