Consolidated Statements of Operations Information for Each of Previous Eight Quarters (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Product revenue	$ 15,393,000	$ 15,153,000	$ 15,551,000	$ 14,335,000	$ 10,350,000	$ 12,184,000	$ 13,014,000	$ 11,934,000	$ 60,431,508	$ 47,482,382	$ 41,834,188
Royalty and other revenue	1,000,000	125,000		1,991,000	5,032,000	6,638,000	4,495,000	4,522,000	3,116,841	20,687,241	20,432,348
Total revenue	16,393,000	15,278,000	15,551,000	16,326,000	15,382,000	18,822,000	17,509,000	16,456,000	63,548,349	68,169,623	62,266,536
Operating expenses:
Cost of product revenue	8,084,000	6,931,000	6,671,000	6,335,000	4,627,000	5,659,000	5,298,000	6,897,000	28,022,034	22,481,122	24,957,243
Cost of royalty and other revenue					738,000	724,000	643,000	577,000		2,682,177	2,213,004
Research and development	1,328,000	1,650,000	1,430,000	1,201,000	1,422,000	1,430,000	2,306,000	2,183,000	5,608,693	7,340,698	10,489,811
Selling, general and administrative	4,975,000	4,471,000	4,326,000	3,384,000	3,367,000	2,902,000	3,124,000	3,308,000	17,154,555	12,701,195	13,226,732
Contingent consideration - fair value adjustments	1,945,000	10,000	18,000	98,000	45,000	65,000	35,000	(54,000)
Gain on bargain purchase	0	0	0	0	0	0	0	0			(314,244)
Total operating expenses	16,332,000	13,062,000	12,445,000	11,018,000	10,199,000	10,780,000	11,406,000	12,911,000	52,857,276	45,296,383	51,183,423
Income from operations	61,000	2,216,000	3,106,000	5,308,000	5,183,000	8,042,000	6,103,000	3,545,000	10,691,073	22,873,240	11,083,113
Investment income	59,000	64,000	85,000	102,000	98,000	76,000	65,000	62,000
Interest expense	(12,000)	(11,000)	(13,000)	(14,000)	(12,000)	(12,000)	(12,000)	(14,000)
Other income (expense)	134,000	(14,000)	65,000	2,000	(54,000)	37,000	(122,000)	29,000	188,000	(110,648)	26,403
Income before income taxes	242,000	2,255,000	3,243,000	5,398,000	5,215,000	8,143,000	6,034,000	3,622,000	11,138,583	23,013,821	11,271,406
Income tax provision	640,000	789,000	418,000	1,121,000	1,887,000	2,255,000	1,495,000	1,284,000	2,968,369	6,920,666	(2,884,631)
Net income	$ (398,000)	$ 1,466,000	$ 2,825,000	$ 4,277,000	$ 3,328,000	$ 5,888,000	$ 4,539,000	$ 2,338,000	$ 8,170,214	$ 16,093,155	$ 14,156,037
Earnings per share:
Basic	$ (0.01)	$ 0.04	$ 0.09	$ 0.13	$ 0.10	$ 0.18	$ 0.14	$ 0.07	$ 0.25	$ 0.51	$ 0.46
Diluted	$ (0.01)	$ 0.04	$ 0.09	$ 0.13	$ 0.10	$ 0.18	$ 0.14	$ 0.07	$ 0.25	$ 0.50	$ 0.45
Weighted average shares outstanding:
Basic	32,747,000	32,677,000	32,234,000	31,963,000	31,916,000	31,858,000	31,644,000	31,241,000	32,497,657	31,667,015	30,914,424
Diluted	32,747,000	33,327,000	33,076,000	31,855,000	32,708,000	32,552,000	32,317,000	31,855,000	33,263,667	32,406,641	31,253,434