Loans and Allowance for Credit Losses - Summary of Loans by Portfolio Class, Including Delinquency Status of those that Continue to Accrue Interest and are Nonperforming (Detail) - USD ($) $ in Millions		Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		$ 379,428	$ 388,213
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		376,824	385,520
Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		1,089	1,230
Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		474	491
Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	1,041	972
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		136,775	135,690
Commercial [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		136,136	135,077
Commercial [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		347	350
Commercial [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		61	94
Commercial [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	231	169
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		54,357	55,487
Commercial Real Estate [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		53,810	55,057
Commercial Real Estate [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		72	87
Commercial Real Estate [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		1	5
Commercial Real Estate [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	474	338
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	114,449	115,845
Residential Mortgages [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	114,028	115,224
Residential Mortgages [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	128	201
Residential Mortgages [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	86	95
Residential Mortgages [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1],[2]	207	325
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		47,221	54,896
Other Retail [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		46,802	54,382
Other Retail [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		235	309
Other Retail [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		55	66
Other Retail [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	129	139
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		26,626	26,295
Credit Card [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		26,048	25,780
Credit Card [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		307	283
Credit Card [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		$ 271	231
Credit Card [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]		$ 1

[1] Substantially all nonperforming loans at June 30, 2023 and December 31, 2022, had an associated allowance for credit losses. The Company recognized interest income on nonperforming loans of $3 million and $5 million for the three months ended June 30, 2023 and 2022, respectively, and $7 million and $8 million for the six months ended June 30, 2023 and 2022, respectively.

[2] At June 30, 2023, $556 million of loans 30–89 days past due and $2.1 billion of loans 90 days or more past due purchased and that could be purchased from Government National Mortgage Association (“GNMA”) mortgage pools under delinquent loan repurchase options whose repayments are insured by the Federal Housing Administration or guaranteed by the United States Department of Veterans Affairs, were classified as current, compared with $647 million and $2.2 billion at December 31, 2022, respectively.