Consolidated Statement of Stockholders' Equity (Unaudited) - 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
Balance, beginning (in shares) at Dec. 31, 2019				25,015,963
Balance, beginning at Dec. 31, 2019		$ 910,472	$ (30)	$ 25	$ 200,179	$ 697,116	$ (30)	$ 13,152
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		(72,534)				(72,534)
Shares repurchased (in shares)				(70,467)
Shares repurchased		(2,741)			(2,741)
Stock based compensation (in shares)				70,597
Stock based compensation		879			879
Dividends on common stock		(8,249)				(8,249)
Change in net unrealized investment appreciation	[1]	4,500						4,500
Change in liability for underfunded employee benefit plans	[2]	847						847
Balance, ending (in shares) at Mar. 31, 2020				25,016,093
Balance, ending at Mar. 31, 2020		833,144		$ 25	198,317	616,303		18,499
Balance, beginning (in shares) at Dec. 31, 2019				25,015,963
Balance, beginning at Dec. 31, 2019		910,472	$ (30)	$ 25	200,179	697,116	$ (30)	13,152
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		(66,574)
Balance, ending (in shares) at Jun. 30, 2020				25,031,234
Balance, ending at Jun. 30, 2020		860,667		$ 25	199,796	613,996		46,850
Balance, beginning (in shares) at Mar. 31, 2020				25,016,093
Balance, beginning at Mar. 31, 2020		833,144		$ 25	198,317	616,303		18,499
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		5,960				5,960
Stock based compensation (in shares)				15,141
Stock based compensation		1,479			1,479
Dividends on common stock		(8,267)				(8,267)
Change in net unrealized investment appreciation	[1]	27,504						27,504
Change in liability for underfunded employee benefit plans	[2]	847						847
Balance, ending (in shares) at Jun. 30, 2020				25,031,234
Balance, ending at Jun. 30, 2020		$ 860,667		$ 25	199,796	613,996		46,850
Balance, beginning (in shares) at Dec. 31, 2020		25,055,479		25,055,479
Balance, beginning at Dec. 31, 2020		$ 825,149		$ 25	202,359	555,854		66,911
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		18,702				18,702
Shares repurchased (in shares)				(207)
Shares repurchased		(7)			(7)
Stock based compensation (in shares)				64,583
Stock based compensation		522			522
Dividends on common stock		(3,767)				(3,767)
Change in net unrealized investment appreciation	[1]	(23,456)						(23,456)
Change in liability for underfunded employee benefit plans	[2]	6,456						6,456
Balance, ending (in shares) at Mar. 31, 2021				25,119,855
Balance, ending at Mar. 31, 2021		$ 823,599		$ 25	202,874	570,789		49,911
Balance, beginning (in shares) at Dec. 31, 2020		25,055,479		25,055,479
Balance, beginning at Dec. 31, 2020		$ 825,149		$ 25	202,359	555,854		66,911
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 32,452
Balance, ending (in shares) at Jun. 30, 2021		25,117,340		25,117,340
Balance, ending at Jun. 30, 2021		$ 839,475		$ 25	203,055	580,767		55,628
Balance, beginning (in shares) at Mar. 31, 2021				25,119,855
Balance, beginning at Mar. 31, 2021		823,599		$ 25	202,874	570,789		49,911
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		13,750				13,750
Shares repurchased (in shares)				(31,027)
Shares repurchased		(1,000)			(1,000)
Stock based compensation (in shares)				28,512
Stock based compensation		1,181			1,181
Dividends on common stock		(3,772)				(3,772)
Change in net unrealized investment appreciation	[1]	7,391						7,391
Change in liability for underfunded employee benefit plans	[2]	$ (1,674)						(1,674)
Balance, ending (in shares) at Jun. 30, 2021		25,117,340		25,117,340
Balance, ending at Jun. 30, 2021		$ 839,475		$ 25	$ 203,055	$ 580,767		$ 55,628

[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 reclassification adjustments and income taxes.