Quarterly Financial Data (Details) (USD $)	3 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, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 14,647,510	$ 14,730,038	$ 13,974,139	$ 15,284,817	$ 22,487,683	$ 17,089,013	$ 16,466,201	$ 19,368,072	$ 58,636,504	$ 75,410,969	$ 82,870,602
Gross profit	11,393,807	10,961,078	10,149,045	10,976,760	16,766,610	12,208,096	11,587,960	14,186,230	43,480,690	54,748,896	61,353,693
Net loss attributable to common stockholders	$ 576,864	$ (2,265,599)	$ (5,207,293)	$ (4,380,445)	$ (2,346,276)	$ (3,568,051)	$ (6,620,586)	$ (2,449,408)	$ (10,932,590)	$ (14,984,321)	$ (23,368,283)
Basic net loss per share attributable to common stockholders (in dollars per share)	$ 0.01	$ (0.05)	$ (0.11)	$ (0.09)	$ (0.05)	$ (0.08)	$ (0.14)	$ (0.05)	$ (0.24)	$ (0.32)	$ (0.50)
Diluted net loss per share attributable to common stockholders (in dollars per share)	$ 0.01	$ (0.05)	$ (0.11)	$ (0.09)	$ (0.05)	$ (0.08)	$ (0.14)	$ (0.05)	$ (0.24)	$ (0.32)	$ (0.50)