Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
Beginning Balance at Dec. 31, 2018	$ 527	$ (125,452)	$ 256,806	$ (453)	$ 1,082,169	$ 1,213,597
Beginning Balance, Shares at Dec. 31, 2018	52,690	4,489
Comprehensive income				(107)	73,243	73,136
Common stock purchased for treasury		$ (10,000)				(10,000)
Common stock acquired, shares		108
Restricted shares forfeited, Shares		11
Share-based compensation	$ 1	$ (8,127)	2,635			(5,491)
Share-based compensation, Shares	149	68
Exercise of stock options	$ 1		1,630			1,631
Exercise of stock options, Shares	83
Ending Balance at Mar. 31, 2019	$ 529	$ (143,579)	261,071	$ (560)	1,155,412	1,272,873
Ending Balance, Shares at Mar. 31, 2019	52,922	4,676
Beginning Balance at Dec. 31, 2019	$ 531	$ (169,365)	270,923		1,341,344	1,443,433
Beginning Balance, Shares at Dec. 31, 2019	53,054	4,949
Comprehensive income					71,385	71,385
Common stock purchased for treasury		$ (60,737)				(60,737)
Common stock acquired, shares		787
Restricted shares forfeited, Shares		10
Share-based compensation	$ 1	$ (4,969)	2,655			(2,313)
Share-based compensation, Shares	164	62
Exercise of stock options			72			72
Exercise of stock options, Shares	3
Ending Balance at Mar. 31, 2020	$ 532	$ (235,071)	$ 273,650		1,408,897	1,448,008
Ending Balance, Shares at Mar. 31, 2020	53,221	5,808
Cumulative effect from the adoption of accounting pronouncements, net of taxes					$ (3,832)	$ (3,832)