Employee Benefits - Asset Allocation (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 283,940	$ 248,735	$ 199,466
Actual % of total	100.00%	100.00%
Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 21,683	$ 21,718
Actual % of total	7.60%	8.70%
Fixed maturity securities - corporate bonds | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Fixed maturity securities - corporate bonds | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	15.00%
Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 4,633	$ 3,534
Actual % of total	1.60%	1.40%
Redeemable preferred stock | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Redeemable preferred stock | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 178,766	$ 149,413
Actual % of total	63.10%	60.00%
Equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	50.00%
Equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	70.00%
Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 23,916	$ 26,266
Actual % of total	8.40%	10.60%
Core plus bond separate account fund | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Core plus bond separate account fund | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	40.00%
U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 27,328	$ 22,269
Actual % of total	9.60%	9.00%
U.S. property separate account fund | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
U.S. property separate account fund | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	25.00%
Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 10,588	$ 9,873
Actual % of total	3.70%	4.00%
Arbitrage fund | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Arbitrage fund | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
United Life annuity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 11,968	$ 11,398
Actual % of total	4.20%	4.60%
United Life annuity | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
United Life annuity | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 5,058	$ 4,264
Actual % of total	1.80%	1.70%
Cash and cash equivalents | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Cash and cash equivalents | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%