Statement of Stockholders' Equity - USD ($) $ in Thousands	Total		Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2018			26,907,000		6,027,000
Beginning balance at Dec. 31, 2018	$ 720,456		$ 269	$ 60,822	$ (91,056)	$ 750,421
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,411					13,411
Stock-based compensation	760			760
Exercise of stock options (in shares)			15,000
Exercise of stock options	431			431
Dividends declared	$ (418)					(418)
Purchase of treasury stock (in shares)	0
Beginning balance (in shares) at Mar. 31, 2019			26,922,000		6,027,000
Beginning balance at Mar. 31, 2019	$ 734,640		$ 269	62,013	$ (91,056)	763,414
Beginning balance (in shares) at Dec. 31, 2019			26,939,000		6,027,000
Beginning balance at Dec. 31, 2019	779,096	[1]	$ 269	63,009	$ (91,056)	806,874
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,607					18,607
Stock-based compensation (in shares)			8,000
Stock-based compensation	460			460
Dividends declared	$ (411)					(411)
Purchase of treasury stock (in shares)	439,112				439,000
Purchase of treasury stock	$ (20,580)				$ (20,580)
Beginning balance (in shares) at Mar. 31, 2020			26,947,000		6,466,000
Beginning balance at Mar. 31, 2020	$ 777,172		$ 269	$ 63,469	$ (111,636)	$ 825,070

[1] The balance sheet at December 31, 2019, as presented, is derived from the audited financial statements at that date.