Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 11,793,909	$ 11,175,440	$ 11,302,667	$ 12,001,499	$ 14,647,510	$ 14,730,038	$ 13,974,139	$ 15,284,817	$ 46,273,515	$ 58,636,504	$ 75,410,969
Gross profit	9,137,575	8,583,096	8,595,004	9,327,124	11,393,807	10,961,078	10,149,045	10,976,760	35,642,799	43,480,690	54,748,896
Net (loss) income attributable to common stockholders	$ (2,827,016)	$ (3,545,218)	$ 1,023,512	$ (3,104,078)	$ 576,864	$ (2,265,599)	$ (5,207,293)	$ (4,380,445)	$ (7,211,821)	$ (10,932,590)	$ (14,984,321)
Basic net (loss) income per share attributable to common stockholders (in dollars per share)	$ (0.06)	$ (0.08)	$ 0.02	$ (0.06)	$ 0.01	$ (0.05)	$ (0.11)	$ (0.09)	$ (0.18)	$ (0.24)	$ (0.32)
Diluted net (loss) income per share attributable to common stockholders (in dollars per share)	$ (0.06)	$ (0.08)	$ 0.02	$ (0.06)	$ 0.01	$ (0.05)	$ (0.11)	$ (0.09)	$ (0.18)	$ (0.24)	$ (0.32)