Consolidated Statements of Stockholders' Equity (Unaudited) Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Beginning balance, common stock, shares issued at Dec. 31, 2019		44,353
Beginning balance, net of taxes at Dec. 31, 2019	$ 701,330	$ 444	$ (138,909)	$ 533,345	$ (50,248)	$ 356,698
Beginning balance, treasury stock, shares at Dec. 31, 2019			5,367
Net income	12,200					12,200
Other comprehensive income (loss)	215				215
Common stock issued, shares		211
Common stock issued, value	2	$ 2
Stock-based compensation	1,674			1,674
Common stock dividends	$ (3,866)					(3,866)
Dividends declared per common share	$ 0.10
Tax withholding payments on stock-based awards	$ (3,309)			(3,309)
Proceeds from exercise of stock options	27			27
Other	(2)			(2)
Ending balance, common stock, shares issued at Mar. 31, 2020		44,564
Ending balance, net of taxes at Mar. 31, 2020	$ 708,271	$ 446	$ (138,909)	531,735	(50,033)	365,032
Ending balance, treasury stock, shares at Mar. 31, 2020			5,367
Beginning balance, common stock, shares issued at Dec. 31, 2020	44,568	44,568
Beginning balance, net of taxes at Dec. 31, 2020	$ 850,799	$ 446	$ (138,909)	538,006	(1,078)	452,334
Beginning balance, treasury stock, shares at Dec. 31, 2020	5,367		5,367
Net income	$ 149,156					149,156
Other comprehensive income (loss)	(4)				(4)
Common stock issued, shares		130
Common stock issued, value	1	$ 1
Stock-based compensation	2,092			2,092
Common stock dividends	$ (4,116)					(4,116)
Dividends declared per common share	$ 0.10
Tax withholding payments on stock-based awards	$ (2,729)			(2,729)
Proceeds from exercise of stock options	63			63
Other	$ (1)			(1)
Ending balance, common stock, shares issued at Mar. 31, 2021	44,698	44,698
Ending balance, net of taxes at Mar. 31, 2021	$ 995,261	$ 447	$ (138,909)	$ 537,431	$ (1,082)	$ 597,374
Ending balance, treasury stock, shares at Mar. 31, 2021	5,367		5,367