Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Other employee benefits	$ 16,358	$ 15,273
Unrealized losses on investments	15,403	0
Deferred revenue	3,710	3,963
Allowance for management fee returned on cancelled policies	3,405	3,330
Pension and other postretirement benefits	0	21,545
Other	3,902	3,484
Total deferred tax assets	42,778	47,595
Deferred tax liabilities:
Depreciation	37,682	35,204
Pension and other postretirement benefits	15,473	0
Prepaid expenses	1,731	2,458
Unrealized gains on investments	0	8,713
Other	1,967	1,075
Total deferred tax liabilities	56,853	47,450
Net deferred tax (liability) asset	(14,075)	0
Net deferred tax (liability) asset	$ 0	$ 145