Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Noninterest income:
Deposit transactions and cash management	$ 42,000	$ 44,000
Fixed income	39,000	73,000
Brokerage, management fees and commissions	22,000	24,000
Card and digital banking fees	20,000	20,000
Other service charges and fees	13,000	13,000
Trust services and investment management	11,000	13,000
Mortgage banking and title income	5,000	22,000
Securities gains (losses), net	0	6,000
Other income	19,000	14,000
Total noninterest income	171,000	229,000
Underwriting, portfolio advisory, and other noninterest income
Noninterest income:
Revenue from contract with customer	10,000	10,000
Regional Banking
Noninterest income:
Deposit transactions and cash management	38,000	39,000
Fixed income	0	0
Brokerage, management fees and commissions	22,000	24,000
Card and digital banking fees	17,000	17,000
Other service charges and fees	8,000	8,000
Trust services and investment management	11,000	13,000
Mortgage banking and title income	0	0
Securities gains (losses), net		0
Other income	11,000	13,000
Total noninterest income	107,000	114,000
Specialty Banking
Noninterest income:
Deposit transactions and cash management	2,000	3,000
Fixed income	39,000	73,000
Brokerage, management fees and commissions	0	0
Card and digital banking fees	1,000	1,000
Other service charges and fees	5,000	5,000
Trust services and investment management	0	0
Mortgage banking and title income	5,000	22,000
Securities gains (losses), net		0
Other income	1,000	1,000
Total noninterest income	53,000	105,000
Corporate
Noninterest income:
Deposit transactions and cash management	2,000	2,000
Fixed income	0	0
Brokerage, management fees and commissions	0	0
Card and digital banking fees	2,000	2,000
Other service charges and fees	0	0
Trust services and investment management	0	0
Mortgage banking and title income	0	0
Securities gains (losses), net		6,000
Other income	7,000	0
Total noninterest income	$ 11,000	$ 10,000