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	Accumulated other comprehensive income Cumulative effect of change in accounting principle
Balance, beginning of year (in shares) at Dec. 31, 2018				25,097,408
Balance, beginning of year at Dec. 31, 2018		$ 888,375	$ (514)	$ 25	$ 203,350	$ 715,472	$ (514)	$ (30,472)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		14,820				14,820
Shares repurchased (in shares)				(258,756)
Shares repurchased		(11,700)			(11,700)
Stock based compensation (in shares)				177,311
Stock based compensation		2,377			2,377
Dividends on common stock		(32,662)				(32,662)
Change in net unrealized investment appreciation	[1]	56,602						56,602
Change in liability for underfunded employee benefit plans	[2]	(12,978)						(12,978)
Compensation expense and related tax benefit for stock-based award grants		6,152			6,152
Balance, ending of year (in shares) at Dec. 31, 2019				25,015,963
Balance, end 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 (loss)		(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		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 (loss)		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

[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.