Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands		Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income, net of tax
Balance, beginning of year (in shares) at Dec. 31, 2016			25,429,769
Balance, beginning of year at Dec. 31, 2016		$ 941,884	$ 25	$ 216,482	$ 616,322	$ 109,055
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		51,023			51,023	0
Shares repurchased (in shares)			(701,899)
Shares repurchased		(29,784)	$ 0	(29,784)	0	0
Stock based compensation (in shares)			188,936
Stock based compensation		4,828	$ 0	4,828	0	0
Dividends on common stock		(27,337)			(27,337)	0
Accumulated effect of change in enacted tax rate		0			(31,308)	31,308
Change in net unrealized investment appreciation	[1]	44,315				44,315
Change in liability for underfunded employee benefit plans	[2]	(16,364)				(16,364)
Compensation expense and related tax benefit for stock-based award grants		4,808		4,808	0	0
Balance, ending of year (in shares) at Dec. 31, 2017			24,916,806
Balance, end of year at Dec. 31, 2017		973,373	$ 25	196,334	608,700	168,314
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		27,650	$ 0	0	27,650	0
Shares repurchased (in shares)			(120,372)
Shares repurchased		(5,404)	$ 0	(5,404)	0	0
Stock based compensation (in shares)			300,974
Stock based compensation		7,171	$ 0	7,171	0	0
Dividends on common stock		(105,408)			(105,408)	0
Change in net unrealized investment appreciation	[1]	(32,944)				(32,944)
Net unrealized investment depreciation of discontinued operations, sold		(6,714)			(6,714)	0
Change in liability for underfunded employee benefit plans	[2]	25,402				25,402
Compensation expense and related tax benefit for stock-based award grants		$ 5,249		5,249	0	0
Balance, ending of year (in shares) at Dec. 31, 2018		25,097,408	25,097,408
Balance, end of year at Dec. 31, 2018		$ 888,375	$ 25	203,350	715,472	(30,472)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		14,820	$ 0	0	14,820	0
Shares repurchased (in shares)			(258,756)
Shares repurchased		(11,700)	$ 0	(11,700)	0	0
Stock based compensation (in shares)			177,311
Stock based compensation		2,377	$ 0	2,377	0	0
Dividends on common stock		(32,662)			(32,662)	0
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	0	0
Balance, ending of year (in shares) at Dec. 31, 2019		25,015,963	25,015,963
Balance, end of year at Dec. 31, 2019		$ 910,472	$ 25	$ 200,179	$ 697,116	$ 13,152

[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.