QUARTERLY FINANCIAL INFORMATION (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Product sales	$ 96,556	$ 87,060	$ 87,470	$ 87,478	$ 92,223	$ 82,602	$ 87,471	$ 88,375	$ 358,564	$ 350,671	$ 338,319
Royalties, fees and other	5,152	4,803	4,600	4,870	4,713	4,338	4,235	4,497	19,425	17,783	16,566
Total revenues	101,708	91,863	92,070	92,348	96,936	86,940	91,706	92,872	377,989	368,454	354,885
Cost of product sales	30,336	28,876	28,724	28,328	27,741	26,204	27,355	26,651	116,264	107,951	103,314
Gross profit	71,372	62,987	63,346	64,020	69,195	60,736	64,351	66,221	261,725	260,503	251,571
Operating expenses:
Research and development	8,428	8,433	8,659	8,445	8,469	8,184	7,899	7,594	33,965	32,146	28,932
Sales and marketing	32,723	29,322	30,218	30,332	29,910	27,175	28,842	30,200	122,595	116,127	108,621
General and administrative	8,537	8,785	8,683	7,458	8,379	8,191	8,154	8,488	33,463	33,212	35,069
Amortization of intangible assets	534	534	505	423	857	1,363	1,316	1,321	1,996	4,857	5,291
Exit costs	695	0	0	0	0	0	(938)	160	695	(778)	8,300
Investigation and restatement-related costs	3,654	3,164	26,335	3,893	6,442	2,139	1,131	1,093	37,046	10,805	80,825
Total operating expenses	54,571	50,238	74,400	50,551	54,057	47,052	46,404	48,856	229,760	196,369	267,038
Income (loss) from operations	16,801	12,749	(11,054)	13,469	15,138	13,684	17,947	17,365	31,965	64,134	(15,467)
Interest and other income (expense), net	(952)	(28)	(392)	522	151	183	(1,147)	386	(850)	(427)	(1,331)
Income (loss) from continuing operations before income taxes	15,849	12,721	(11,446)	13,991	15,289	13,867	16,800	17,751	31,115	63,707	(16,798)
Income tax provision (benefit)	4,471	2,449	(4,667)	2,806	4,118	3,882	4,536	4,793	5,059	17,329	(13,985)
Net income (loss) from operations	11,378	10,272	(6,779)	11,185	11,171	9,985	12,264	12,958	26,056	46,378	(2,813)
Accrued dividend and accretion charges on Series A 3% Redeemable Convertible Preferred Stock	(947)	(940)	(929)	(919)	(909)	(900)	(887)	(879)	(3,735)	(3,575)	(3,416)
Net income (loss) attributable to common stockholders	10,431	9,332	(7,708)	10,266	10,262	9,085	11,377	12,079	22,321	42,803	(4,318)
Other comprehensive income
Foreign currency adjustments	133	1,131	(344)	(1,099)	120	951	(778)	392	(179)	685	369
Total comprehensive income (loss)	$ 11,511	$ 11,403	$ (7,123)	$ 10,086	$ 11,291	$ 10,936	$ 11,486	$ 13,350	$ 25,877	$ 47,063	$ (533)
Weighted-average shares outstanding:
Basic (in shares)	28,480	28,374	28,081	28,055	27,912	27,714	27,639	27,614	28,311	27,752	27,382
Diluted (in shares)	29,160	28,968	28,722	28,785	28,341	28,087	27,934	27,987	28,988	28,407	27,382
Earnings per share applicable to common stockholders:
Basic (in dollars per share)	$ 0.30	$ 0.27	$ (0.27)	$ 0.31	$ 0.30	$ 0.27	$ 0.34	$ 0.36	$ 0.65	$ 1.28	$ (0.16)
Diluted (in dollars per share)	$ 0.30	$ 0.27	$ (0.27)	$ 0.30	$ 0.30	$ 0.27	$ 0.34	$ 0.36	$ 0.64	$ 1.25	$ (0.16)