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		Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		$ 387,866	$ 388,213
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		385,020	385,520
Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		1,213	1,230
Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		494	491
Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		1,139	972
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		137,326	135,690
Commercial [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		136,619	135,077
Commercial [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		457	350
Commercial [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		72	94
Commercial [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		178	169
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		55,158	55,487
Commercial Real Estate [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		54,544	55,057
Commercial Real Estate [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		74	87
Commercial Real Estate [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		5	5
Commercial Real Estate [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	535	338
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	116,948	115,845
Residential Mortgages [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	116,411	115,224
Residential Mortgages [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	148	201
Residential Mortgages [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	97	95
Residential Mortgages [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1],[2]	292	325
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		52,945	54,896
Other Retail [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		52,494	54,382
Other Retail [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		254	309
Other Retail [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		64	66
Other Retail [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	133	139
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		25,489	26,295
Credit Card [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		24,952	25,780
Credit Card [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		280	283
Credit Card [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		256	231
Credit Card [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	$ 1	$ 1

[1] Substantially all nonperforming loans at March 31, 2023 and December 31, 2022, had an associated allowance for credit losses. The Company recognized interest income on nonperforming loans of $4 million and $3 million for the three months ended March 31, 2023 and 2022, respectively.

[2] At March 31, 2023, $542 million of loans 30–89 days past due and $2.2 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.