Product Revenue by Geographic Location and Percentage of Total Product Revenue (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	$ 14,055,440	$ 17,756,000	$ 46,551,045	$ 44,230,840
Percentage of revenue	100.00%	100.00%	100.00%	100.00%
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	11,911,946	13,233,998	38,317,667	33,170,393
Percentage of revenue	85.00%	75.00%	82.00%	75.00%
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	1,069,661	2,512,690	3,937,427	6,887,323
Percentage of revenue	7.00%	14.00%	9.00%	16.00%
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	$ 1,073,833	$ 2,009,312	$ 4,295,951	$ 4,173,124
Percentage of revenue	8.00%	11.00%	9.00%	9.00%