Consolidated Statements of Operations Information for Each of Previous Eight Quarters (Detail) (USD $)	3 Months Ended								9 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, 2011	Dec. 31, 2010	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue:
Product revenue	$ 10,350,000	$ 12,184,000	$ 13,014,000	$ 11,934,000	$ 9,710,000	$ 11,123,000	$ 11,659,000	$ 9,342,000	$ 13,215,053	$ 11,810,869	$ 47,482,382	$ 41,834,188
Royalty and other revenue	5,032,000	6,638,000	4,495,000	4,522,000	9,104,000	3,981,000	3,865,000	3,482,000	10,235,194	9,573,770	20,687,241	20,432,348
Total revenue	15,382,000	18,822,000	17,509,000	16,456,000	18,814,000	15,104,000	15,524,000	12,824,000	23,450,247	21,384,639	68,169,623	62,266,536
Operating expenses:
Cost of product revenue	4,627,000	5,659,000	5,298,000	6,897,000	5,920,000	6,419,000	7,345,000	5,273,000	5,157,135	4,186,670	22,481,122	24,957,243
Cost of royalty and other revenue	738,000	724,000	643,000	577,000	620,000	594,000	537,000	462,000	1,315,315	1,160,775	2,682,177	2,213,004
Research and development	1,422,000	1,430,000	2,306,000	2,183,000	2,343,000	2,433,000	2,906,000	2,808,000	9,461,960	8,744,548	7,340,698	10,489,811
Selling, general and administrative	3,367,000	2,902,000	3,124,000	3,308,000	3,253,000	3,126,000	3,418,000	3,428,000	9,050,382	5,580,215	12,701,195	13,226,732
Contingent consideration - fair value adjustments	45,000	65,000	35,000	(54,000)	267,000	344,000					91,191	610,877
Gain on bargain purchase								(314,000)	(427,478)			(314,244)
Total operating expenses	10,199,000	10,780,000	11,406,000	12,911,000	12,403,000	12,916,000	14,206,000	11,657,000	24,557,314	19,672,208	45,296,383	51,183,423
Income from operations	5,183,000	8,042,000	6,103,000	3,545,000	6,411,000	2,188,000	1,318,000	1,167,000	(1,107,067)	1,712,431	22,873,240	11,083,113
Investment income	98,000	76,000	65,000	62,000	62,000	95,000	29,000	31,000
Interest income (expense)	(12,000)	(12,000)	(12,000)	(14,000)	(14,000)	7,000	(27,000)	(22,000)
Other income (expense)	(54,000)	37,000	(122,000)	29,000	(41,000)	(500,000)	458,000	109,000	(623,094)		(110,648)	26,403
Income (loss) before income taxes	5,215,000	8,143,000	6,034,000	3,622,000	6,418,000	1,790,000	1,778,000	1,285,000	(1,596,881)	1,987,178	23,013,821	11,271,406
Income tax provision (benefit)	1,887,000	2,255,000	1,495,000	1,284,000	(3,135,000)	(16,000)	208,000	59,000	15,744		6,920,666	(2,884,631)
Net income	$ 3,328,000	$ 5,888,000	$ 4,539,000	$ 2,338,000	$ 9,553,000	$ 1,806,000	$ 1,570,000	$ 1,226,000	$ (1,612,625)	$ 1,987,178	$ 16,093,155	$ 14,156,037	$ (1,612,625)
Earnings per share:
Basic	$ 0.10	$ 0.18	$ 0.14	$ 0.07	$ 0.31	$ 0.06	$ 0.05	$ 0.04	$ (0.05)	$ 0.06	$ 0.51	$ 0.46
Diluted	$ 0.10	$ 0.18	$ 0.14	$ 0.07	$ 0.30	$ 0.06	$ 0.05	$ 0.04	$ (0.05)	$ 0.06	$ 0.50	$ 0.45
Weighted average shares outstanding:
Basic	31,916,000	31,858,000	31,644,000	31,241,000	31,132,000	30,948,000	30,845,000	30,730,000	30,774,467	30,778,430	31,667,015	30,914,424
Diluted	32,708,000	32,552,000	32,317,000	31,855,000	31,600,000	31,256,000	31,149,000	31,010,000	30,774,467	30,949,264	32,406,641	31,253,434