Income Taxes - Sources of Difference and Tax Effects (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Sources of the difference and the tax effects
Federal income tax expense, at statutory rate	$ 34,496	$ 36,702	$ 25,973
Investment income, net	(1,060)	(1,394)	(1,626)
State taxes, net	11	211	34
Nondeductible expenses	613	697	488
Tax windfall related to share-based stock compensation	(101)	(298)	(1,003)
Other, net	(399)	641	214
Total income tax expense	$ 33,560	$ 36,559	$ 24,080