Loans and Allowance for Credit Losses - Activity in Allowance for Credit Losses by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 6,155	$ 8,010
Provision for credit losses	112	(827)
Loans charged-off	280	374
Less recoveries of loans charged-off	(118)	(151)
Net loan charge-offs (recoveries)	162	223
Balance at end of period	6,105	6,960
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,849	2,423
Provision for credit losses	19	(435)
Loans charged-off	55	86
Less recoveries of loans charged-off	(23)	(30)
Net loan charge-offs (recoveries)	32	56
Balance at end of period	1,836	1,932
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,123	1,544
Provision for credit losses	(54)	(19)
Loans charged-off	1	10
Less recoveries of loans charged-off	(6)	(17)
Net loan charge-offs (recoveries)	(5)	(7)
Balance at end of period	1,074	1,532
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	565	573
Provision for credit losses	29	(39)
Loans charged-off	5	5
Less recoveries of loans charged-off	(11)	(10)
Net loan charge-offs (recoveries)	(6)	(5)
Balance at end of period	600	539
Other Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	945	1,115
Provision for credit losses	40	(75)
Loans charged-off	61	83
Less recoveries of loans charged-off	(32)	(48)
Net loan charge-offs (recoveries)	29	35
Balance at end of period	956	1,005
Credit Card [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	1,673	2,355
Provision for credit losses	78	(259)
Loans charged-off	158	190
Less recoveries of loans charged-off	(46)	(46)
Net loan charge-offs (recoveries)	112	144
Balance at end of period	$ 1,639	$ 1,952