Commitments and Credit Risk (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Other Commitments [Line Items]
Commitments to originate fixed-rate mortgage loans, term	30 days
Outstanding letters of credit	$ 993,200,000	$ 785,400,000
Term of letter of credit	1 year	1 year
Standby Letters of Credit
Other Commitments [Line Items]
Outstanding letters of credit	$ 71,000,000.0	$ 72,900,000
Deferred revenue	$ 0	$ 0
Standby Letters of Credit | Minimum
Other Commitments [Line Items]
Term of letter of credit	9 months	9 months
Standby Letters of Credit | Maximum
Other Commitments [Line Items]
Term of letter of credit	15 years	15 years
Credit Card Commitments
Other Commitments [Line Items]
Outstanding commitments	$ 800,400,000	$ 799,400,000
Other Loan Commitments
Other Commitments [Line Items]
Outstanding commitments	4,400,000,000	4,190,000,000
Fixed Rate Mortgage Loans
Other Commitments [Line Items]
Outstanding commitments	$ 28,400,000	$ 20,500,000