Condensed Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 295,949	$ 283,148
Cost of sales	158,334	143,275
Gross profit	137,615	139,873
Selling, general and administrative expenses	105,037	113,951
Income from operations	32,578	25,922
Foreign currency gains (losses), net	(1,217)	1,071
Interest income	195	279
Interest expense	(1,817)	(113)
Other income, net	590	53
Income before income taxes	30,329	27,212
Income tax expense	5,619	10,758
Net income	24,710	16,454
Dividends on Series A convertible preferred stock	0	(3,000)
Dividend equivalents on Series A convertible preferred stock related to redemption value accretion and beneficial conversion feature	0	(931)
Net income attributable to common stockholders	$ 24,710	$ 12,523
Net income per common share:
Basic (in dollars per share)	$ 0.34	$ 0.15
Diluted (in dollars per share)	$ 0.33	$ 0.15
Weighted average common shares outstanding:
Basic (shares)	73,009	68,705
Diluted (shares)	74,875	71,668