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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 6,105	$ 6,960	$ 6,155	$ 8,010
Provision for credit losses	311	(170)	423	(997)
Loans charged-off	276	314	556	688
Less recoveries of loans charged-off	(115)	(134)	(233)	(285)
Net loan charge-offs (recoveries)	161	180	323	403
Balance at end of period	6,255	6,610	6,255	6,610
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,836	1,932	1,849	2,423
Provision for credit losses	90	(67)	109	(502)
Loans charged-off	53	58	108	144
Less recoveries of loans charged-off	(23)	(31)	(46)	(61)
Net loan charge-offs (recoveries)	30	27	62	83
Balance at end of period	1,896	1,838	1,896	1,838
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,074	1,532	1,123	1,544
Provision for credit losses	(95)	(123)	(149)	(142)
Loans charged-off	9	4	10	14
Less recoveries of loans charged-off	(3)	(4)	(9)	(21)
Net loan charge-offs (recoveries)	6		1	(7)
Balance at end of period	973	1,409	973	1,409
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	600	539	565	573
Provision for credit losses	49	(71)	78	(110)
Loans charged-off	2	5	7	10
Less recoveries of loans charged-off	(11)	(15)	(22)	(25)
Net loan charge-offs (recoveries)	(9)	(10)	(15)	(15)
Balance at end of period	658	478	658	478
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	956	1,005	945	1,115
Provision for credit losses	42	4	82	(71)
Loans charged-off	50	55	111	138
Less recoveries of loans charged-off	(34)	(40)	(66)	(88)
Net loan charge-offs (recoveries)	16	15	45	50
Balance at end of period	982	994	982	994
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,639	1,952	1,673	2,355
Provision for credit losses	225	87	303	(172)
Loans charged-off	162	192	320	382
Less recoveries of loans charged-off	(44)	(44)	(90)	(90)
Net loan charge-offs (recoveries)	118	148	230	292
Balance at end of period	$ 1,746	$ 1,891	$ 1,746	$ 1,891