Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 6,255	$ 6,610	$ 6,155	$ 8,010
Provision for credit losses	362	(163)	785	(1,160)
Loans charged-off	275	266	831	954
Less recoveries of loans charged-off	(113)	(119)	(346)	(404)
Net loan charge-offs (recoveries)	162	147	485	550
Balance at end of period	6,455	6,300	6,455	6,300
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,896	1,838	1,849	2,423
Provision for credit losses	97	(75)	206	(577)
Loans charged-off	56	40	164	184
Less recoveries of loans charged-off	(29)	(26)	(75)	(87)
Net loan charge-offs (recoveries)	27	14	89	97
Balance at end of period	1,966	1,749	1,966	1,749
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	973	1,409	1,123	1,544
Provision for credit losses	(7)	(104)	(156)	(246)
Loans charged-off		14	10	28
Less recoveries of loans charged-off	(6)	(1)	(15)	(22)
Net loan charge-offs (recoveries)	(6)	13	(5)	6
Balance at end of period	972	1,292	972	1,292
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	658	478	565	573
Provision for credit losses	38	3	116	(107)
Loans charged-off	2	3	9	13
Less recoveries of loans charged-off	(7)	(13)	(29)	(38)
Net loan charge-offs (recoveries)	(5)	(10)	(20)	(25)
Balance at end of period	701	491	701	491
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	982	994	945	1,115
Provision for credit losses	12	36	94	(35)
Loans charged-off	56	55	167	193
Less recoveries of loans charged-off	(29)	(36)	(95)	(124)
Net loan charge-offs (recoveries)	27	19	72	69
Balance at end of period	967	1,011	967	1,011
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,746	1,891	1,673	2,355
Provision for credit losses	222	(23)	525	(195)
Loans charged-off	161	154	481	536
Less recoveries of loans charged-off	(42)	(43)	(132)	(133)
Net loan charge-offs (recoveries)	119	111	349	403
Balance at end of period	$ 1,849	$ 1,757	$ 1,849	$ 1,757