Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs in the Past Twelve Months that have Subsequently Defaulted (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($) SecurityLoan	Sep. 30, 2022 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,561	6,741
Amount Defaulted | $	$ 58	$ 121
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	186	575
Amount Defaulted | $	$ 15	$ 21
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	5	10
Amount Defaulted | $	$ 6	$ 8
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	67	180
Amount Defaulted | $	$ 8	$ 18
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	73	216
Amount Defaulted | $	$ 1	$ 3
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,117	5,478
Amount Defaulted | $	$ 11	$ 29
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,448	6,459
Amount Defaulted | $	$ 41	$ 79
Government National Mortgage Association [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	113	282
Amount Defaulted | $	$ 17	$ 42