Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands		Total	Cumulative effect of change in accounting principle	Common Stock	Additional paid-in capital	Retaining earnings	Retaining earnings Cumulative effect of change in accounting principle	Accumulated other comprehensive income (loss)
Balance, beginning of year (in shares) at Dec. 31, 2019				25,015,963
Balance, beginning of year at Dec. 31, 2019		$ 910,472	$ (30)	$ 25	$ 200,179	$ 697,116	$ (30)	$ 13,152
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		(112,706)				(112,706)
Shares repurchased (in shares)				(70,467)
Shares repurchased		(2,741)			(2,741)
Stock based compensation (in shares)				109,983
Stock based compensation		(71)			(71)
Dividends on common stock		(28,526)				(28,526)
Change in net unrealized investment appreciation	[1]	35,791						35,791
Change in liability for underfunded employee benefit plans	[2]	17,968						17,968
Compensation expense and related tax benefit for stock-based award grants		4,992			4,992
Balance, ending of year (in shares) at Dec. 31, 2020				25,055,479
Balance, end of year at Dec. 31, 2020		825,149		$ 25	202,359	555,854		66,911
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		80,594				80,594
Shares repurchased (in shares)				(67,651)
Shares repurchased		(2,007)			(2,007)
Stock based compensation (in shares)				94,276
Stock based compensation		3,023			3,023
Dividends on common stock		(15,064)				(15,064)
Change in net unrealized investment appreciation	[1]	(33,301)						(33,301)
Change in liability for underfunded employee benefit plans	[2]	$ 20,727						20,727
Balance, ending of year (in shares) at Dec. 31, 2021		25,082,104		25,082,104
Balance, end of year at Dec. 31, 2021		$ 879,121		$ 25	203,375	621,384		54,337
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		15,031				15,031
Stock based compensation (in shares)				128,437
Stock based compensation		3,655			3,655
Dividends on common stock		(15,860)				(15,860)
Change in net unrealized investment appreciation	[1]	(138,138)						(138,138)
Change in liability for underfunded employee benefit plans	[2]	$ (3,695)						(3,695)
Balance, ending of year (in shares) at Dec. 31, 2022		25,210,541		25,210,541
Balance, end of year at Dec. 31, 2022		$ 740,114		$ 25	$ 207,030	$ 620,555		$ (87,496)

[1] The change in net unrealized appreciation is net of reclassification adjustments and income taxes.

[2] The change in liability for underfunded employee benefit plans is net of income taxes.