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	16,377		16,377
Dividends paid	(2,618)		(2,618)
Repurchases of common stock (in shares)		0
Repurchases of common stock	(86)		(86)
Exercise of stock appreciation rights (in shares)		2
Exercise of stock appreciation rights	(1)		(1)
Share-based compensation expense related to stock appreciation rights	259		259
Accumulated postretirement benefit obligation adjustment, net of tax	180			180
Net unrealized gain (loss) on investments	(4,157)			(4,157)
Balance, end of period, shares at Sep. 30, 2022		1,897
Balance, end of period at Sep. 30, 2022	239,041	$ 0	239,792	(751)
Balance, beginning of period, shares at Jun. 30, 2022		1,897
Balance, beginning of period at Jun. 30, 2022	233,179	$ 0	232,759	420
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	7,913		7,913
Dividends paid	(873)		(873)
Repurchases of common stock (in shares)		0
Repurchases of common stock	(86)		(86)
Share-based compensation expense related to stock appreciation rights	79		79
Accumulated postretirement benefit obligation adjustment, net of tax	13			13
Net unrealized gain (loss) on investments	(1,184)			(1,184)
Balance, end of period, shares at Sep. 30, 2022		1,897
Balance, end of period at Sep. 30, 2022	239,041	$ 0	239,792	(751)
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	15,850		15,850
Dividends paid	(2,616)		(2,616)
Repurchases of common stock (in shares)		(7)
Repurchases of common stock	(959)		(959)
Exercise of stock appreciation rights (in shares)		1
Exercise of stock appreciation rights	0		0
Share-based compensation expense related to stock appreciation rights	337		337
Accumulated postretirement benefit obligation adjustment, net of tax	100			100
Net unrealized gain (loss) on investments	(1,055)			(1,055)
Balance, end of period, shares at Sep. 30, 2023		1,891
Balance, end of period at Sep. 30, 2023	252,668	$ 0	253,423	(755)
Balance, beginning of period, shares at Jun. 30, 2023		1,891
Balance, beginning of period at Jun. 30, 2023	247,253	$ 0	247,092	161
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	7,084		7,084
Dividends paid	(870)		(870)
Share-based compensation expense related to stock appreciation rights	117		117
Accumulated postretirement benefit obligation adjustment, net of tax	(6)			(6)
Net unrealized gain (loss) on investments	(910)			(910)
Balance, end of period, shares at Sep. 30, 2023		1,891
Balance, end of period at Sep. 30, 2023	$ 252,668	$ 0	$ 253,423	$ (755)