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, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 332,369	$ 312,028
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	330,407	309,520
Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	814	1,202
Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	423	472
Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	725	834
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	125,983	112,023
Commercial [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	125,490	111,270
Commercial [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	254	530
Commercial [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	91	49
Commercial [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	148	174
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	39,753	39,053
Commercial Real Estate [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	39,519	38,678
Commercial Real Estate [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	24	80
Commercial Real Estate [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4	11
Commercial Real Estate [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	206	284
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	82,114	76,493
Residential Mortgages [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	81,689	75,962
Residential Mortgages [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	100	124
Residential Mortgages [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	102	181
Residential Mortgages [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	223	226
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	60,822	61,959
Other Retail [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	60,376	61,468
Other Retail [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	236	275
Other Retail [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	62	66
Other Retail [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	148	150
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	23,697	22,500
Credit Card [Member] | Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	23,333	22,142
Credit Card [Member] | Accruing 30-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	200	193
Credit Card [Member] | Accruing 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 164	$ 165