Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following table represents the fair value hierarchy for our financial assets and liabilities measured at fair value on a recurring basis:

	As of December 31, 2016
	Level 1		Level 2		Level 3		Balance
Financial Assets
Cash equivalents	$	11,972,733	$	141,869,024	$	-	$	153,841,757
Short-term investments		-		66,810,962		-		66,810,962
Total financial assets measured at fair value	$	11,972,733	$	208,679,986	$	-	$	220,652,719
Financial Liabilities
Current portion of derivative instruments related to stock purchase warrants	$	-	$	-	$	1,465,272	$	1,465,272
Total financial liabilities measured at fair value	$	-	$	-	$	1,465,272	$	1,465,272

	As of December 31, 2015
	Level 1		Level 2		Level 3		Balance
Financial Assets
Cash equivalents	$	6,430,561	$	-	$	-	$	6,430,561
Total financial assets measured at fair value	$	6,430,561	$	-	$	-	$	6,430,561
Financial Liabilities
Current portion of derivative instruments related to stock purchase warrants	$	-	$	-	$	16,411	$	16,411
Non-current portion of derivative instruments related to stock purchase warrants		-		-		491,791		491,791
Total financial liabilities measured at fair value	$	-	$	-	$	508,202	$	508,202

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following table sets forth a summary of changes in the fair value of the Company’s Level 3 liabilities for the years ended December 31, 2016, 2015 and 2014: 

					Exercised
	Balance as of		Unrealized		Stock Purchase		Balance as of
	December 31,		Losses		Warrants		December 31,
Description	2015		2016		2016		2016
Derivative liabilities related to stock purchase warrants	$	508,202	$	957,070	$	-	$	1,465,272

					Exercised
	Balance as of		Unrealized		Stock Purchase		Balance as of
	December 31,		(Gains)		Warrants		December 31,
Description	2014		2015		2015		2015
Derivative liabilities related to stock purchase warrants	$	807,679	$	(299,477)	$	-	$	508,202

					Exercised
	Balance as of		Unrealized		Stock Purchase		Balance as of
	December 31,		(Gains)		Warrants		December 31,
Description	2013		2014		2014		2014
Derivative liabilities related to stock purchase warrants	$	1,740,235	$	(508,817)	$	(423,739)	$	807,679

Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]

Quantitative Information about Level 3 Fair Value Measurements
Fair Value at December 31, 2016		Valuation  Technique	Unobservable Inputs
$	1,465,272	Black-Scholes option-pricing model	Expected term
			Expected dividends
			Anticipated volatility