Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Financial Assets or Liabilities Measured at Fair Value on Recurring Basis

In accordance with the fair value hierarchy, the following table shows the fair value as of March 31, 2014 and December 31, 2013 of those financial assets and liabilities that are measured at fair value on a recurring basis, according to the valuation techniques the Company used to determine their fair value. No financial assets or liabilities are measured at fair value on a nonrecurring basis at March 31, 2014 and December 31, 2013.

	Quoted Prices in Active Markets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)		Fair Value
As of March 31, 2014:
Cash equivalents
Money market funds	$	3,707,423	$	—	$	—	$	3,707,423
Municipal bonds		—		1,100,000		—		1,100,000
Short- and long-term investments
US government obligations		—		500,239		—		500,239
Corporate commercial paper, stock, bonds and notes		25,919,865		28,514,690		—		54,434,555
Total assets at fair value	$	29,627,288	$	30,114,929	$	—	$	59,742,217
Warrant liability		—		—		625,163		625,163
Total liabilities at fair value	$	—	$	—	$	625,163	$	625,163

	Quoted Prices in Active Markets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)		Fair Value
As of December 31, 2013:
Cash equivalents
Money market funds	$	5,535,716	$	—	$	—	$	5,535,716
Corporate commercial paper, bonds and notes		—		1,749,983		—		1,749,983
Municipal bonds		—		1,110,000		—		1,110,000
Short- and long-term investments
US government obligations		—		1,151,932		—		1,151,932
Corporate commercial paper, stock, bonds and notes		20,176,154		36,984,932		—		57,161,086
Total assets at fair value	$	25,711,870	$	40,996,847	$	—	$	66,708,717
Warrant liability		—		—		716,786		716,786
Total liabilities at fair value	$	—	$	—	$	716,786	$	716,786

Fair Value of Warrant Liability

The following table rolls forward the fair value of the Company’s warrant liability, the fair value of which is determined by Level 3 inputs for the three months ended March 31, 2014 and 2013:

Balance at December 31, 2013	$	716,786
Change in fair value for the three months ended March 31, 2014		(91,623	)
Balance at March 31, 2014	$	625,163
Balance at December 31, 2012	$	1,488,179
Change in fair value for the three months ended March 31, 2013		(301,260	)
Balance at March 31, 2013	$	1,186,919