Revenue from Contracts with Customers - Summary of Sources of Noninterest Income that are Subject to Revenue Recognition Accounting Guidance (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 394	$ 360	$ 1,149	$ 1,119
Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	132	121	383	354
Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	170	155	500	521
Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	32	27	91	76
Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	41	43	121	122
Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	19	14	54	46
Commercial Bank
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	69	67	205	190
Commercial Bank | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	40	38	120	109
Commercial Bank | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	1	0	3	1
Commercial Bank | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	2	1	5	4
Commercial Bank | Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	18	21	54	57
Commercial Bank | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	8	7	23	19
Retail Bank
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	123	112	353	333
Retail Bank | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	92	83	263	245
Retail Bank | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Retail Bank | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Retail Bank | Merchant discount and credit card interchange fees
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	23	22	67	65
Retail Bank | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	8	7	23	23
Institutional Services and Wealth Management
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	202	181	591	596
Institutional Services and Wealth Management | Service charges on deposit accounts
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Institutional Services and Wealth Management | Trust income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	169	155	497	520
Institutional Services and Wealth Management | Brokerage services income
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	30	26	86	72
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	0
Institutional Services and Wealth Management | Other
Disaggregation Of Revenue [Line Items]
Revenue from contract with customer	$ 3	$ 0	$ 8	$ 4