Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income
Balance, beginning of period, shares at Dec. 31, 2020		1,892
Balance, beginning of period at Dec. 31, 2020	$ 200,422	$ 0	$ 196,096	$ 4,326
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,823		13,823
Dividends paid	(832)		(832)
Stock options and stock appreciation rights exercised (in shares)		2
Exercise of stock appreciation rights	(1)		(1)
Share-based compensation expense related to stock appreciation rights	71		71
Adjustments to postretirement benefits obligation, net of deferred tax expense of $(46) and $0 for March 31, 2022 and 2021, respectively	0
Net unrealized gain (loss) on investments	(610)			(610)
Balance, end of period, shares at Mar. 31, 2021		1,894
Balance, end of period at Mar. 31, 2021	212,873	$ 0	209,157	3,716
Balance, beginning of period, shares at Dec. 31, 2021		1,895
Balance, beginning of period at Dec. 31, 2021	229,087	$ 0	225,861	3,226
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,185		6,185
Dividends paid	(873)		(873)
Stock options and stock appreciation rights exercised (in shares)		2
Exercise of stock appreciation rights	(1)		(1)
Share-based compensation expense related to stock appreciation rights	102		102
Adjustments to postretirement benefits obligation, net of deferred tax expense of $(46) and $0 for March 31, 2022 and 2021, respectively	(173)			(173)
Net unrealized gain (loss) on investments	(2,181)			(2,181)
Balance, end of period, shares at Mar. 31, 2022		1,897
Balance, end of period at Mar. 31, 2022	$ 232,492	$ 0	$ 231,274	$ 1,218