Revenue by Geographic Location and Percentage of Total Revenue (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 20,828,377	$ 19,624,769	$ 36,075,388	$ 33,985,429
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	15,482,068	16,728,331	27,765,515	27,835,044
Percentage of total revenue	74.00%	85.00%	77.00%	82.00%
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	1,986,195	1,128,126	3,569,963	2,929,543
Percentage of total revenue	10.00%	6.00%	10.00%	9.00%
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 3,360,114	$ 1,768,312	$ 4,739,910	$ 3,220,842
Percentage of total revenue	16.00%	9.00%	13.00%	9.00%