Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Type (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,449	$ 4,612	$ 4,537	$ 4,733
Provision for credit losses	311	298	941	1,063
Loans charged off	410	450	1,264	1,505
Less recoveries of loans charged off	(74)	(122)	(238)	(352)
Net loans charged off	336	328	1,026	1,153
Other changes	(10)	(4)	(38)	(65)
Balance at end of period	4,414	4,578	4,414	4,578
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,111	1,023	1,075	1,051
Provision for credit losses	83	19	210	64
Loans charged off	80	65	219	184
Less recoveries of loans charged off	(22)	(54)	(70)	(100)
Net loans charged off	58	11	149	84
Other changes
Balance at end of period	1,136	1,031	1,136	1,031
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	725	777	776	857
Provision for credit losses	(6)	(22)	(64)	(100)
Loans charged off	10	17	27	76
Less recoveries of loans charged off	(6)	(23)	(30)	(80)
Net loans charged off	4	(6)	(3)	(4)
Other changes
Balance at end of period	715	761	715	761
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	848	921	875	935
Provision for credit losses	(13)	70	74	222
Loans charged off	48	62	171	243
Less recoveries of loans charged off	(6)	(5)	(15)	(20)
Net loans charged off	42	57	156	223
Other changes
Balance at end of period	793	934	793	934
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	874	874	884	863
Provision for credit losses	162	151	495	495
Loans charged off	174	175	546	559
Less recoveries of loans charged off	(16)	(15)	(48)	(66)
Net loans charged off	158	160	498	493
Other changes			(3)
Balance at end of period	878	865	878	865
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	779	838	781	848
Provision for credit losses	84	84	227	305
Loans charged off	96	122	291	412
Less recoveries of loans charged off	(23)	(24)	(73)	(83)
Net loans charged off	73	98	218	329
Other changes
Balance at end of period	790	824	790	824
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,337	4,433	4,391	4,554
Provision for credit losses	310	302	942	986
Loans charged off	408	441	1,254	1,474
Less recoveries of loans charged off	(73)	(121)	(236)	(349)
Net loans charged off	335	320	1,018	1,125
Other changes			(3)
Balance at end of period	4,312	4,415	4,312	4,415
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	112	179	146	179
Provision for credit losses	1	(4)	(1)	77
Loans charged off	2	9	10	31
Less recoveries of loans charged off	(1)	(1)	(2)	(3)
Net loans charged off	1	8	8	28
Other changes	(10)	(4)	(35)	(65)
Balance at end of period	$ 102	$ 163	$ 102	$ 163