Commitments and Credit Risk (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Other Commitments [Line Items]
Commitments to originate fixed-rate mortgage loans, term	30 days
Outstanding letters of credit	$ 837,600,000	$ 580,800,000
Investment, Type [Extensible Enumeration]	Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]	Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]
Term of letter of credit	1 year	1 year
Standby Letters of Credit
Other Commitments [Line Items]
Outstanding letters of credit	$ 55,700,000	$ 54,200,000
Deferred revenue	$ 0	$ 0
Minimum | Standby Letters of Credit
Other Commitments [Line Items]
Term of letter of credit	9 months	9 months
Maximum | Standby Letters of Credit
Other Commitments [Line Items]
Term of letter of credit	15 years	15 years
Credit Card Commitments
Other Commitments [Line Items]
Outstanding commitments	$ 751,700,000	$ 738,200,000
Other Loan Commitments
Other Commitments [Line Items]
Outstanding commitments	4,140,000,000	4,170,000,000
Fixed Rate Mortgage Loans
Other Commitments [Line Items]
Outstanding commitments	$ 30,200,000	$ 16,600,000