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	6 Months Ended
	Jun. 30, 2023 USD ($) SecurityLoan	Jun. 30, 2023 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,163	4,180
Amount Defaulted | $	$ 38	$ 63
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	175	389
Amount Defaulted | $	$ 3	$ 6
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2	5
Amount Defaulted | $	$ 1	$ 2
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	79	113
Amount Defaulted | $	$ 7	$ 10
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	60	143
Amount Defaulted | $	$ 1	$ 2
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	1,727	3,361
Amount Defaulted | $	$ 9	$ 18
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,043	4,011
Amount Defaulted | $	$ 21	$ 38
Government National Mortgage Association [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	120	169
Amount Defaulted | $	$ 17	$ 25