Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Fixed income	$ 205	$ 406	$ 423
Deposit transactions and cash management	171	175	148
Brokerage, management fees and commissions	92	88	66
Card and digital banking fees	84	78	60
Mortgage banking and title income	68	154	129
Other service charges and fees	54	44	26
Trust services and investment management	48	51	39
Securities gains (losses), net	18	13	(6)
Purchase accounting gain	0	(1)	533
Other income (loss)	75	68	74
Total noninterest income	815	1,076	1,492
Underwriting, Portfolio Advisory, and Other Noninterest Income
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	43	44	39
Regional Banking
Disaggregation of Revenue [Line Items]
Fixed income	0	0	1
Deposit transactions and cash management	153	157	131
Brokerage, management fees and commissions	92	88	66
Card and digital banking fees	75	67	50
Mortgage banking and title income	0	0	0
Other service charges and fees	32	23	18
Trust services and investment management	48	51	39
Securities gains (losses), net	0	0	0
Purchase accounting gain		0	0
Other income (loss)	44	52	40
Total noninterest income	444	438	345
Specialty Banking
Disaggregation of Revenue [Line Items]
Fixed income	205	406	422
Deposit transactions and cash management	10	12	11
Brokerage, management fees and commissions	0	0	0
Card and digital banking fees	2	3	2
Mortgage banking and title income	68	152	128
Other service charges and fees	22	17	7
Trust services and investment management	0	0	0
Securities gains (losses), net	0	0	0
Purchase accounting gain		0	0
Other income (loss)	4	7	6
Total noninterest income	311	597	576
Corporate
Disaggregation of Revenue [Line Items]
Fixed income	0	0	0
Deposit transactions and cash management	8	6	6
Brokerage, management fees and commissions	0	0	0
Card and digital banking fees	7	8	8
Mortgage banking and title income	0	2	1
Other service charges and fees	0	4	1
Trust services and investment management	0	0	0
Securities gains (losses), net	18	13	(6)
Purchase accounting gain		(1)	533
Other income (loss)	27	9	28
Total noninterest income	$ 60	$ 41	$ 571