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, 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	8,464		8,464
Dividends paid	(1,745)		(1,745)
Exercise of stock appreciation rights (in shares)		2
Exercise of stock appreciation rights	(1)		(1)
Share-based compensation expense related to stock appreciation rights	180		180
Accumulated postretirement benefit obligation adjustment	167			167
Net unrealized gain (loss) on investments	(2,973)			(2,973)
Balance, end of period, shares at Jun. 30, 2022		1,897
Balance, end of period at Jun. 30, 2022	233,179	$ 0	232,759	420
Balance, beginning of period, shares at Mar. 31, 2022		1,897
Balance, beginning of period at Mar. 31, 2022	232,492	$ 0	231,274	1,218
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,279		2,279
Dividends paid	(872)		(872)
Share-based compensation expense related to stock appreciation rights	78		78
Accumulated postretirement benefit obligation adjustment	(6)			(6)
Net unrealized gain (loss) on investments	(792)			(792)
Balance, end of period, shares at Jun. 30, 2022		1,897
Balance, end of period at Jun. 30, 2022	233,179	$ 0	232,759	420
Balance, beginning of period, shares at Dec. 31, 2022		1,897
Balance, beginning of period at Dec. 31, 2022	241,011	$ 0	240,811	200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,766		8,766
Dividends paid	(1,746)		(1,746)
Repurchases of common stock (in shares)		(7)
Repurchases of common stock	(959)
Exercise of stock appreciation rights (in shares)		1
Exercise of stock appreciation rights	0
Share-based compensation expense related to stock appreciation rights	220		220
Accumulated postretirement benefit obligation adjustment	106			106
Net unrealized gain (loss) on investments	(145)			(145)
Balance, end of period, shares at Jun. 30, 2023		1,891
Balance, end of period at Jun. 30, 2023	247,253	$ 0	247,092	161
Balance, beginning of period, shares at Mar. 31, 2023		1,898
Balance, beginning of period at Mar. 31, 2023	241,838	$ 0	241,278	560
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	7,585		7,585
Dividends paid	(873)		(873)
Repurchases of common stock (in shares)		(7)
Repurchases of common stock	(959)		(959)
Share-based compensation expense related to stock appreciation rights	61		61
Accumulated postretirement benefit obligation adjustment	(5)			(5)
Net unrealized gain (loss) on investments	(394)			(394)
Balance, end of period, shares at Jun. 30, 2023		1,891
Balance, end of period at Jun. 30, 2023	$ 247,253	$ 0	$ 247,092	$ 161