Debt - Summary of Debt (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Nov. 23, 2015
Long-term debt
Long-term debt	$ 253,600,000	$ 302,300,000
Total	$ 502,600,000	437,300,000
FHLB advances interest rate	0.00%
Bank Credit Facility
Short-term debt
Bank Credit Facility	$ 249,000,000	135,000,000.0
4.50% Senior Notes
Long-term debt
Long-term debt	$ 248,600,000	248,300,000
Interest Rates	4.50%		4.50%
Principal amount	$ 250,000,000.0		$ 250,000,000
Unamortized discount	300,000	400,000
Unamortized debt issuance costs	1,100,000	1,300,000
Federal Home Loan Bank borrowing
Long-term debt
Long-term debt	$ 5,000,000.0	$ 54,000,000.0