Condensed Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenues	$ 313,221	$ 323,828	$ 581,128	$ 602,968
Cost of sales	143,414	154,188	277,737	303,962
Gross profit	169,807	169,640	303,391	299,006
Selling, general and administrative expenses	140,361	149,035	258,363	264,158
Income from operations	29,446	20,605	45,028	34,848
Foreign currency gain (loss), net	162	(1,700)	438	(2,947)
Interest income	157	164	307	380
Interest expense	(188)	(234)	(372)	(477)
Other income (loss)	9	(189)	133	(107)
Income before income taxes	29,586	18,646	45,534	31,697
Income tax expense	7,627	3,109	12,564	6,014
Net income	21,959	15,537	32,970	25,683
Dividends on Series A convertible preferred stock	(3,000)	(3,000)	(6,000)	(6,000)
Dividend equivalents on Series A convertible preferred shares related to redemption value accretion and beneficial conversion feature	(873)	(802)	(1,729)	(1,587)
Net income attributable to common stockholders	$ 18,086	$ 11,735	$ 25,241	$ 18,096
Net income per common share:
Basic (in dollars per share)	$ 0.21	$ 0.13	$ 0.29	$ 0.21
Diluted (in dollars per share)	$ 0.20	$ 0.13	$ 0.29	$ 0.20
Weighted average common shares outstanding - basic (shares)	73,953	73,389	73,882	73,238
Weighted average common shares outstanding - diluted (shares)	74,572	74,243	74,625	74,389