Consolidated Statements of Operations Information for Each of Previous Eight Quarters (Detail) (USD $)	3 Months Ended								9 Months Ended		12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Revenue:
Product revenue	$ 9,710,000	$ 11,123,000	$ 11,659,000	$ 9,342,000	$ 3,114,000	$ 5,742,000	$ 4,359,000	$ 3,150,000	$ 13,215,053	$ 11,810,869	$ 41,834,188		$ 14,961,397
Royalty and other revenue	9,104,000	3,981,000	3,865,000	3,482,000	4,051,000	2,889,000	3,295,000	2,756,000	10,235,194	9,573,770	20,432,348		12,329,627
Total revenue	18,814,000	15,104,000	15,524,000	12,824,000	7,165,000	8,631,000	7,654,000	5,906,000	23,450,247	21,384,639	62,266,536		27,291,024
Operating expenses:
Cost of product revenue	5,920,000	6,419,000	7,345,000	5,273,000	1,511,000	2,093,000	1,553,000	1,393,000	5,157,135	4,186,670	24,957,243		5,579,759
Cost of royalty and other revenue	620,000	594,000	537,000	462,000	481,000	418,000	416,000	376,000	1,315,315	1,160,775	2,213,004		1,537,666
Research and development	2,343,000	2,433,000	2,906,000	2,808,000	2,870,000	3,075,000	3,517,000	3,785,000	9,461,960	8,744,548	10,489,811		12,528,819
Selling, general and administrative	3,253,000	3,126,000	3,418,000	3,428,000	4,268,000	2,493,000	2,289,000	2,438,000	9,050,382	5,580,215	13,226,732		8,018,851
Contingent consideration - fair value adjustments	267,000	344,000			(427,000)						610,877
Gain on bargain purchase				(314,000)	(427,000)				(427,478)		(314,244)
Total operating expenses	12,403,000	12,916,000	14,206,000	11,657,000	8,703,000	8,079,000	7,775,000	7,992,000	24,557,314	19,672,208	51,183,423		27,665,095
Income (loss) from operations	6,411,000	2,188,000	1,318,000	1,167,000	(1,538,000)	552,000	(121,000)	(2,086,000)	(1,107,067)	1,712,431	11,083,113		(374,071)
Investment income	62,000	95,000	29,000	31,000	43,000	53,000	66,000	69,000
Interest expense	(14,000)	7,000	(27,000)	(22,000)	(28,000)			(13,000)	(27,773)	(12,683)	(56,714)		(26,167)
Other income (expense)	(41,000)	(500,000)	458,000	109,000	(623,000)				(623,094)		26,403
Income (loss) before income taxes	6,418,000	1,790,000	1,778,000	1,285,000	(2,146,000)	605,000	(55,000)	(2,030,000)	(1,596,881)	1,987,178	11,271,406	(1,596,881)	(43,509)
Income tax provision (benefit)	(3,135,000)	(16,000)	208,000	59,000	16,000				15,744		(2,884,631)	15,774
Net income (loss)	$ 9,553,000	$ 1,806,000	$ 1,570,000	$ 1,226,000	$ (2,162,000)	$ 605,000	$ (55,000)	$ (2,030,000)	$ (1,612,625)	$ 1,987,178	$ 14,156,037		$ (43,509)
Earnings (loss) per share:
Basic	$ 0.31	$ 0.06	$ 0.05	$ 0.04	$ (0.07)	$ 0.02	$ 0.00	$ (0.06)	$ (0.05)	$ 0.06	$ 0.46		$ 0.00
Diluted	$ 0.30	$ 0.06	$ 0.05	$ 0.04	$ (0.07)	$ 0.02	$ 0.00	$ (0.06)	$ (0.05)	$ 0.06	$ 0.45		$ 0.00
Weighted average shares outstanding:
Basic	31,132,000	30,948,000	30,845,000	30,730,000	30,715,000	30,797,000	30,812,000	30,782,000	30,774,467	30,778,430	30,914,424		30,781,881
Diluted	31,600,000	31,256,000	31,149,000	31,010,000	30,715,000	30,934,000	30,812,000	30,782,000	30,774,467	30,949,264	31,253,434		30,781,881