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 ($) SecurityLoan	Sep. 30, 2021 USD ($) SecurityLoan	Sep. 30, 2022 USD ($) SecurityLoan	Sep. 30, 2021 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,561	2,490	6,741	7,254
Amount Defaulted | $	$ 58	$ 27	$ 121	$ 98
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	186	244	575	856
Amount Defaulted | $	$ 15	$ 5	$ 21	$ 29
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	5	4	10	16
Amount Defaulted | $	$ 6	$ 1	$ 8	$ 7
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	67	20	180	47
Amount Defaulted | $	$ 8	$ 2	$ 18	$ 5
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	73	124	216	595
Amount Defaulted | $	$ 1	$ 2	$ 3	$ 10
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,117	2,069	5,478	5,638
Amount Defaulted | $	$ 11	$ 12	$ 29	$ 32
Total loans, excluding loans purchased from GNMA mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	2,448	2,461	6,459	7,152
Amount Defaulted | $	$ 41	$ 22	$ 79	$ 83
Loans purchased from GNMA mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	113	29	282	102
Amount Defaulted | $	$ 17	$ 5	$ 42	$ 15