Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) segment subsidiary	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Property, Plant and Equipment
Deficiency (benefit) of stock-based compensation plans	$ 300,000	$ 200,000	$ (500,000)
Impairment losses	$ 0	0	0
Number of significant subsidiaries | subsidiary	1
Income tax examination, penalties	$ 0	0	0
Cash on deposit with Federal Reserve Bank	199,000,000	518,900,000
Federal Reserve Bank stock	94,200,000	93,600,000
Federal Home Loan Bank stock	127,800,000	103,800,000
Advertising expense	900,000	3,800,000	$ 2,600,000
Loans and Leases Receivable Disclosure [Line Items]
Accrued interest receivable	129,100,000	118,300,000
Accrued Investment Income Receivable	38,500,000	38,900,000
Hosting Arrangement, Service Contract, Implementation Cost, Expense, Amortization	$ 2,300,000	3,400,000
Number of operating segments | segment	1
Total investment securities	$ 1,200,000	1,200,000
Buildings and improvements | Minimum
Property, Plant and Equipment
Estimated useful lives	5 years
Buildings and improvements | Maximum [Member]
Property, Plant and Equipment
Estimated useful lives	45 years
Furniture and equipment | Minimum
Property, Plant and Equipment
Estimated useful lives	3 years
Furniture and equipment | Maximum [Member]
Property, Plant and Equipment
Estimated useful lives	15 years
Loans
Loans and Leases Receivable Disclosure [Line Items]
Accrued interest receivable	$ 86,100,000	$ 76,500,000