Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Treasury Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Dec. 31, 2016		(19,304)
Beginning Balance at Dec. 31, 2016	$ 1,481,598	$ (352,742)	$ 45,376	$ 254,512	$ 1,534,983	$ (531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends	(7,995)				(7,995)
Stock-Based Compensation (in shares)		3
Stock-Based Compensation	25,830	$ 48		25,782
Reissued Shares (in shares)		529
Reissued Shares	(2,720)	$ 7,531		(10,251)
Repurchased Shares (in shares)		(1,961)
Repurchased Shares	(62,550)	$ (62,550)
Net Earnings (Loss)	292,536				292,536
Foreign Currency Translation Adjustment	1,305					1,305
Ending Balance (in shares) at Dec. 31, 2017		(20,733)
Ending Balance at Dec. 31, 2017	1,728,004	$ (407,713)	45,376	270,043	1,819,524	774
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends	(8,661)				(8,661)
Stock-Based Compensation	26,852			26,852
Reissued Shares (in shares)		915
Reissued Shares	(9,372)	$ 8,601		(17,973)
Repurchased Shares (in shares)		(3,750)
Repurchased Shares	(168,735)	$ (168,735)
Net Earnings (Loss)	196,210				196,210
Foreign Currency Translation Adjustment	(1,861)					(1,861)
Ending Balance (in shares) at Dec. 31, 2018		(23,568)
Ending Balance at Dec. 31, 2018	1,760,708	$ (567,847)	45,376	278,922	2,005,344	(1,087)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends	(9,795)				(9,795)
Stock-Based Compensation	25,758			25,758
Reissued Shares (in shares)		690
Reissued Shares	(5,289)	$ 9,162		(14,451)
Repurchased Shares (in shares)		(1,156)
Repurchased Shares	(69,255)	$ (69,255)
Net Earnings (Loss)	31,472				31,472
Foreign Currency Translation Adjustment	1,068					1,068
Ending Balance (in shares) at Dec. 31, 2019		(24,034)
Ending Balance at Dec. 31, 2019	$ 1,737,259	$ (627,940)	$ 45,376	$ 290,229	$ 2,029,613	$ (19)