Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Noninterest income:
Fixed income	$ 73	$ 126
Deposit transactions and cash management	44	42
Brokerage, management fees and commissions	24	20
Mortgage banking and title income	22	53
Card and digital banking fees	20	17
Trust services and investment management	13	12
Other service charges and fees	13	10
Securities gains (losses), net	6
Other income	14	18
Total noninterest income	229	298
Regional Banking
Noninterest income:
Fixed income	0	1
Deposit transactions and cash management	39	38
Brokerage, management fees and commissions	24	20
Mortgage banking and title income	0	0
Card and digital banking fees	17	14
Trust services and investment management	13	12
Other service charges and fees	8	6
Securities gains (losses), net	0
Other income	13	9
Total noninterest income	114	100
Specialty Banking
Noninterest income:
Fixed income	73	125
Deposit transactions and cash management	3	3
Brokerage, management fees and commissions	0	0
Mortgage banking and title income	22	52
Card and digital banking fees	1	1
Trust services and investment management	0	0
Other service charges and fees	5	3
Securities gains (losses), net	0
Other income	1	1
Total noninterest income	105	185
Corporate
Noninterest income:
Fixed income	0	0
Deposit transactions and cash management	2	1
Brokerage, management fees and commissions	0	0
Mortgage banking and title income	0	1
Card and digital banking fees	2	2
Trust services and investment management	0	0
Other service charges and fees	0	1
Securities gains (losses), net	6
Other income	0	8
Total noninterest income	10	13
Underwriting, portfolio advisory, and other noninterest income
Noninterest income:
Revenue from contract with customer	$ 10	$ 10