Product Revenue by Geographic Location and Percentage of Total Product Revenue (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	$ 14,494,489	$ 13,613,328
Percentage of revenue	100.00%	100.00%
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	11,566,779	10,390,045
Percentage of revenue	80.00%	76.00%
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	1,547,914	1,770,752
Percentage of revenue	11.00%	13.00%
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Product revenue	$ 1,379,796	$ 1,452,531
Percentage of revenue	9.00%	11.00%