Condensed Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues	$ 283,148	$ 267,907
Cost of sales	143,275	134,323
Gross profit	139,873	133,584
Selling, general and administrative expenses	113,951	118,002
Income from operations	25,922	15,582
Foreign currency gains, net	1,071	276
Interest income	279	150
Interest expense	(113)	(184)
Other income, net	53	124
Income before income taxes	27,212	15,948
Income tax expense	10,758	4,938
Net income	16,454	11,010
Dividends on Series A convertible preferred stock	(3,000)	(3,000)
Dividend equivalents on Series A convertible preferred shares related to redemption value accretion and beneficial conversion feature	(931)	(855)
Net income attributable to common stockholders	$ 12,523	$ 7,155
Net income per common share:
Basic (in dollars per share)	$ 0.15	$ 0.08
Diluted (in dollars per share)	$ 0.15	$ 0.08
Weighted average common shares outstanding - basic (shares)	68,705	73,810
Weighted average common shares outstanding - diluted (shares)	71,668	74,561