Fair Value (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table classifies the Company’s financial assets and liabilities measured at fair value on a recurring basis at December 31, 2015 and 2014, respectively into the fair value hierarchy:

	Balance at December 31, 2015
	Level 1		Level 2		Level 3		Total
Asset included in:
Cash and cash equivalents
Money market securities	$	3,290,490	$	—	$	—	$	3,290,490
Available-for-sale investments at fair value
U.S. government obligations	$	3,298,014	$	—	$	—	$	3,298,014
U.S. government agency obligations	$	—	$	14,589,378	$	—	$	14,589,378
Corporate debt securities	$	—	$	12,918,016	$	—	$	12,918,016

	Balance at December 31, 2014
	Level 1		Level 2		Level 3		Total
Asset included in:
Cash and cash equivalents
Money market securities	$	3,608,890	$	—	$	—	$	3,608,890
Liabilities included in:
Warrant liabilities
Growth Term Loan warrants	$	—	$	—	$	301,508	$	301,508
Convertible Preferred Stock warrants	$	—	$	—	$	429,035	$	429,035

Summary of Fair Value Assessment of Warrant Liability Inputs using Black Sholes Option Pricing Model

The December 31, 2014 fair value assessments used the Black-Sholes option pricing model using the following assumptions:

	December 31, 2014
Fair value of Series B/C/D Stock and Series E Stock shares    on grant date or measurement date	$0.14 - $0.22
Exercise price	$0.01-$0.346
Expected risk-free interest rate		1.20%
Expected volatility		70%
Expected term	4.1 years
Expected dividend yield	0 - 8%

Reconciliation of Beginning and Ending Liabilities Measured at Fair Value on Recurring Basis

A reconciliation of the beginning and ending liabilities measured at fair value and classified as Level 3 for the years ended December 31, 2015 and 2014 are as follows:

	December 31,
	2015			2014
Beginning balance	$	730,543		$	44,120
Issuance of Series E Convertible Preferred Stock Warrants		—			2,190,708
Exercise of Series E Convertible Preferred Stock Warrants		(4,116	)		(1,889,201	)
Exercise of Series D Convertible Preferred Stock Warrants		(91,798	)		(4,020	)
Reclassification of Series C-2 Convertible Preferred Stock    Warrants to Common Stock Warrants		(555	)		—
Reclassification of Growth Term Loan Warrants to    Common Stock Warrants		(229,550	)		—
Issuance of Convertible Note Warrants		741,828			—
Reclassification of Convertible Note Warrants to    Common Stock Warrants		(1,386,035	)		—
Change in Convertible Preferred Stock warrant valuation		239,683			388,936
Ending balance	$	—		$	730,543