Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

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

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

	As of March 31, 2017
	Level 1		Level 2		Level 3		Balance
Financial Assets
Cash equivalents	$	16,160,498	$	-	$	-	$	16,160,498
Total financial assets measured at fair value	$	16,160,498	$	-	$	-	$	16,160,498

	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

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 three months ended March 31, 2017 and 2016:

					Exercised
	Balance as of		Unrealized		Stock Purchase		Balance as of
	December 31,		Losses		Warrants		March 31,
Description	2016		2017		2017		2017
Derivative liabilities related to stock purchase warrants	$	1,465,272	$	90,191	$	(1,555,463)	$	-

					Exercised
	Balance as of		Unrealized		Stock Purchase		Balance as of
	December 31,		(Gains)		Warrants		March 31,
Description	2015		2016		2016		2016
Derivative liabilities related to stock purchase warrants	$	508,202	$	(39,898)	$	-	$	468,304