Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) segment subsidiary	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Property, Plant and Equipment
Deficiency (benefit) of stock-based compensation plans	$ 200,000	$ (500,000)	$ (400,000)
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	518,900,000	2,166,100,000
Federal Reserve Bank stock	93,600,000	42,800,000
Federal Home Loan Bank stock	103,800,000	10,600,000
Advertising expense	3,800,000	2,600,000	$ 2,800,000
Loans and Leases Receivable Disclosure [Line Items]
Accrued interest receivable	118,300,000	47,400,000
Accrued Investment Income Receivable	38,900,000	16,600,000
Hosting Arrangement, Service Contract, Implementation Cost, Expense, Amortization	$ 3,400,000	4,600,000
Number of operating segments | segment	1
Total investment securities	$ 1,200,000	400,000
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	$ 76,500,000	$ 30,200,000