Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Type (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,351	$ 4,497	$ 4,375	$ 4,537
Provision for credit losses	281	324	545	630
Loans charged off	380	432	763	854
Less recoveries of loans charged off	(84)	(83)	(188)	(164)
Net loans charged off	296	349	575	690
Other changes	(10)	(23)	(19)	(28)
Balance at end of period	4,326	4,449	4,326	4,449
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,200	1,091	1,146	1,075
Provision for credit losses	22	75	120	127
Loans charged off	65	76	139	139
Less recoveries of loans charged off	(23)	(21)	(54)	(48)
Net loans charged off	42	55	85	91
Other changes			(1)
Balance at end of period	1,180	1,111	1,180	1,111
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	721	742	726	776
Provision for credit losses	15	(21)	(8)	(58)
Loans charged off	9	9	14	17
Less recoveries of loans charged off	(8)	(13)	(31)	(24)
Net loans charged off	1	(4)	(17)	(7)
Balance at end of period	735	725	735	725
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	764	862	787	875
Provision for credit losses	6	43	18	87
Loans charged off	41	62	82	123
Less recoveries of loans charged off	(8)	(5)	(14)	(9)
Net loans charged off	33	57	68	114
Balance at end of period	737	848	737	848
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	871	884	880	884
Provision for credit losses	171	163	325	333
Loans charged off	190	188	372	372
Less recoveries of loans charged off	(21)	(18)	(40)	(32)
Net loans charged off	169	170	332	340
Other changes		(3)		(3)
Balance at end of period	873	874	873	874
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	738	785	771	781
Provision for credit losses	65	63	88	143
Loans charged off	75	95	156	195
Less recoveries of loans charged off	(24)	(26)	(49)	(50)
Net loans charged off	51	69	107	145
Balance at end of period	752	779	752	779
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,294	4,364	4,310	4,391
Provision for credit losses	279	323	543	632
Loans charged off	380	430	763	846
Less recoveries of loans charged off	(84)	(83)	(188)	(163)
Net loans charged off	296	347	575	683
Other changes		(3)	(1)	(3)
Balance at end of period	4,277	4,337	4,277	4,337
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	57	133	65	146
Provision for credit losses	2	1	2	(2)
Loans charged off		2		8
Less recoveries of loans charged off				(1)
Net loans charged off		2		7
Other changes	(10)	(20)	(18)	(25)
Balance at end of period	$ 49	$ 112	$ 49	$ 112