Consolidated Statements of Operations Information for Each of Previous Eight Quarters (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Product revenue	$ 25,500	$ 24,677	$ 29,170	$ 25,094	$ 21,449	$ 19,814	$ 21,457	$ 20,816	$ 104,441	$ 83,537	$ 60,431
Royalty and other revenue	100								100		3,117
Total revenue	25,600	24,677	29,170	25,094	21,449	19,814	21,457	20,816	104,541	83,537	63,548
Operating expenses:
Cost of product revenue	12,162	11,242	12,644	11,069	10,148	8,444	8,586	8,073	47,117	35,251	28,022
Cost of royalty and other revenue	0	0	0	0	0	0	0	0	0	0	0
Research and development	2,040	1,886	1,890	1,539	1,431	1,490	1,252	1,568	7,355	5,740	5,609
Selling, general and administrative	8,568	7,127	8,140	7,018	6,473	5,959	6,242	6,024	30,853	24,699	17,154
Contingent consideration - fair value adjustments	(75)	675	637	2,005	1,969	233	768	1,112	3,242	4,083	2,072
Total operating expenses	22,695	20,930	23,311	21,631	20,021	16,126	16,848	16,777	88,567	69,773	52,857
Income from operations	2,905	3,747	5,859	3,463	1,428	3,688	4,609	4,039	15,974	13,764	10,691
Investment income	112	97	76	61	44	37	19	36	346	136	309
Interest expense	(1,570)	(1,555)	(638)	(5)	(8)	(8)	(8)	(9)	(3,768)	(32)	(50)
Other income (expense)	119	(75)	75	(979)	(270)	(38)	(269)	132	(860)	(445)	188
Income before income taxes	1,566	2,214	5,372	2,540	1,194	3,679	4,351	4,198	11,692	13,423	11,138
Income tax provision (benefit)	3,463	1,059	1,500	915	929	1,141	738	1,269	11	4,078	2,968
Net income (loss)	$ 5,029	$ 1,155	$ 3,872	$ 1,625	$ 265	$ 2,538	$ 3,613	$ 2,929	$ 11,681	$ 9,345	$ 8,170
Earnings per share:
Basic	$ 0.15	$ 0.03	$ 0.12	$ 0.05	$ 0.01	$ 0.08	$ 0.11	$ 0.09	$ 0.35	$ 0.28	$ 0.25
Diluted	$ 0.15	$ 0.03	$ 0.11	$ 0.05	$ 0.01	$ 0.08	$ 0.11	$ 0.09	$ 0.34	$ 0.28	$ 0.25
Weighted average shares outstanding:
Basic	33,833,000	33,779,000	33,649,000	33,025,000	32,946,000	32,925,000	32,870,000	32,755,000	33,572,883	32,881,940	32,497,657
Diluted	34,369,000	34,313,000	34,175,000	33,494,000	33,577,000	33,690,000	33,671,000	33,451,000	34,098,898	33,577,091	33,263,667