CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Net sales	$ 249,646	$ 281,123	$ 537,402	$ 566,221
Cost of sales	153,994	170,470	311,314	331,197
Gross profit	95,652	110,653	226,088	235,024
Operating expenses:
Selling expense	61,672	75,711	129,980	152,549
General and administrative expense	15,169	18,446	29,756	30,680
Research and development expense	7,333	6,930	14,746	14,403
Total operating expenses	84,174	101,087	174,482	197,632
Income from operations	11,478	9,566	51,606	37,392
Other income (expense), net	28	(4,571)	4,029	(887)
Income before income taxes	11,506	4,995	55,635	36,505
Income tax provision	1,435	2,196	3,904	1,904
Net income	10,071	2,799	51,731	34,601
Dividends on convertible preferred stock	783	2,625	1,566	5,250
Net income allocable to common shareholders	$ 9,288	$ 174	$ 50,165	$ 29,351
Earnings per common share:
Basic	$ 0.13	$ 0.00	$ 0.71	$ 0.45
Diluted	$ 0.12	$ 0.00	$ 0.59	$ 0.41
Weighted-average common shares outstanding:
Basic	71,111	65,060	71,086	65,021
Diluted	86,349	65,112	92,235	84,950