Revenue from Contracts with Customers - Summary of Sources of Noninterest Income that are Subject to Revenue Recognition Guidance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 1,541	$ 1,484	$ 1,525
Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	514	475	447
Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	675	680	741
Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	121	102	88
Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	162	161	159
Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	69	66	90
Commercial Bank
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	272	257	232
Commercial Bank | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	160	144	130
Commercial Bank | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	3	2	0
Commercial Bank | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	6	6	5
Commercial Bank | Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	74	77	73
Commercial Bank | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	29	28	24
Retail Bank
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	471	444	431
Retail Bank | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	353	330	317
Retail Bank | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0
Retail Bank | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0
Retail Bank | Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	88	84	86
Retail Bank | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	30	30	28
Institutional Services and Wealth Management
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	798	783	862
Institutional Services and Wealth Management | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	1	1	0
Institutional Services and Wealth Management | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	672	678	741
Institutional Services and Wealth Management | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	115	96	83
Institutional Services and Wealth Management | Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0
Institutional Services and Wealth Management | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 10	$ 8	$ 38