Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation expense
Total stock based compensation expense	$ 1,406,131	$ 920,799
Options vested in period, fair value	971,488	1,526,211
Research and Development Expense
Stock-based compensation expense
Total stock based compensation expense	395,709	372,200
Cost of Revenue
Stock-based compensation expense
Total stock based compensation expense	39,631	26,156
Included in selling, general and administrative expense
Stock-based compensation expense
Total stock based compensation expense	970,791	601,309
Benefit from restructuring
Stock-based compensation expense
Total stock based compensation expense	0	(78,866)
Stock Option
Stock-based compensation expense
Unrecognized compensation cost	$ 2,662,066	$ 5,677,247
Weighted-average remaining vesting period for recognition	1 year 9 months 15 days	2 years 7 months 10 days
Options outstanding, weighted average contractual life	8 years 26 days