Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 4,366	$ 4,320	$ 4,357	$ 4,306
Provision for credit losses	350	327	695	657
Loans charged-off	437	407	854	812
Less recoveries of loans charged-off	(97)	(90)	(179)	(180)
Net loans charged-off	340	317	675	632
Other changes	1	(1)		(2)
Balance at end of period	4,377	4,329	4,377	4,329
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,429	1,441	1,450	1,287
Provision for credit losses	44	111	98	348
Loans charged-off	104	107	200	218
Less recoveries of loans charged-off	(26)	(28)	(47)	(56)
Net loans charged-off	78	79	153	162
Balance at end of period	1,395	1,473	1,395	1,473
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	842	734	812	724
Provision for credit losses	5	14	33	19
Loans charged-off	2	7	5	10
Less recoveries of loans charged-off	(11)	(7)	(16)	(15)
Net loans charged-off	(9)		(11)	(5)
Balance at end of period	856	748	856	748
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	485	556	510	631
Provision for credit losses	(22)	5	(35)	(51)
Loans charged-off	16	25	33	48
Less recoveries of loans charged-off	(8)	(8)	(13)	(12)
Net loans charged-off	8	17	20	36
Balance at end of period	455	544	455	544
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	622	678	617	743
Provision for credit losses	85	16	150	5
Loans charged-off	88	79	177	159
Less recoveries of loans charged-off	(29)	(28)	(58)	(54)
Net loans charged-off	59	51	119	105
Balance at end of period	648	643	648	643
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	955	875	934	883
Provision for credit losses	239	179	450	336
Loans charged-off	227	189	439	377
Less recoveries of loans charged-off	(23)	(19)	(45)	(43)
Net loans charged-off	204	170	394	334
Other changes				(1)
Balance at end of period	990	884	990	884
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	4,333	4,284	4,323	4,268
Provision for credit losses	351	325	696	657
Loans charged-off	437	407	854	812
Less recoveries of loans charged-off	(97)	(90)	(179)	(180)
Net loans charged-off	340	317	675	632
Other changes				(1)
Balance at end of period	4,344	4,292	4,344	4,292
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	33	36	34	38
Provision for credit losses	(1)	2	(1)
Other changes	1	(1)		(1)
Balance at end of period	$ 33	$ 37	$ 33	$ 37