Interim Consolidated Statements of Shareholders' Equity and Comprehensive Income (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2018	$ 590,063	$ 448	$ 764,717	$ (3,814,604)	$ 3,941,916	$ (302,414)
Beginning balance, shares at Dec. 31, 2018		24,921,963
Exercise of stock options and restricted stock units, shares	171,752	171,752
Share based compensation, exercise value	$ (28,990)		(751)	(28,257)	(18)	0
Repurchases of common stock	$ (186,250)			(186,250)
Repurchases of common stock, shares	(290,429)	(290,429)
Adjustment to Additional Paid in Capital, Share-Based Compensation	$ 4,482		4,482
Net Income (Loss) Attributable to Parent	111,805				111,805
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	12,660					12,660
Ending balance at Mar. 31, 2019	561,750	$ 448	769,950	(3,972,597)	4,053,703	(289,754)
Ending balance, shares at Mar. 31, 2019		24,803,286
Beginning balance at Dec. 31, 2019	$ 420,780	$ 448	783,871	(4,539,154)	4,499,288	(323,673)
Beginning balance, shares at Dec. 31, 2019	24,125,317	24,125,317
Exercise of stock options and restricted stock units, shares	50,372	50,372
Share based compensation, exercise value	$ (7,135)		0	(9,355)	(2,220)	0
Repurchases of common stock	$ (200,000)			(200,000)
Repurchases of common stock, shares	(268,161)	(268,161)
Adjustment to Additional Paid in Capital, Share-Based Compensation	$ 4,395		4,395
Net Income (Loss) Attributable to Parent	98,115				98,115
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(24,028)					(24,028)
Ending balance at Mar. 31, 2020	$ 306,397	$ 448	$ 788,266	$ (4,729,799)	$ 4,595,183	$ (347,701)
Ending balance, shares at Mar. 31, 2020	23,907,528	23,907,528