Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Summary of Financial Instruments Measured at Fair Value on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):

	Fair Value Measurements at December 31, 2016
	Total		Level 1		Level 2	Level 3
Assets
Money market fund	$	2,563,247	$	2,563,247	—	—
Liabilities
Series A warrant liability	194,048		194,048		—	—
Series C warrant liability	85,490		—		—	85,490
Total common stock warrant liability	$	279,538	$	194,048	—	$	85,490
	Fair Value Measurements at December 31, 2015
	Total		Level 1		Level 2	Level 3
Assets
Money market fund	$	3,803,929	$	3,803,929	—	—
Liabilities
Series A warrant liability	1,212,803		1,212,803		—	—
Series B warrant liability	865,000		—		—	865,000
Series C warrant liability	462,437		—		—	462,437
Total common stock warrant liability	$	2,540,240	$	1,212,803	—	$	1,327,437

Summary of Changes in Fair Value of Level1 and Level 3 Financial Instruments

The following table sets forth a summary of the changes in the fair value of the Company’s Level 1 and Level 3 financial instruments, which are treated as liabilities, as follows:

	Series A Warrant				Series B Warrant					Series C Warrant
	Number of Warrants	Liability			Number of Warrants		Liability			Number of Warrants	Liability
Balance at December 31, 2015	2,425,605	$	1,212,803		116,580		$	865,000		590,415	$	462,437
Change in value of Series A Warrants	—	(1,018,755		)	—		—			—	—
De-recognition of Series B Warrant liability upon cashless exercise of warrants (485,202 shares issued)	—	—			(102,300	)	(593,584		)	—	—
De-recognition of Series B Warrant liability upon expiration	—	—			(14,280	)	—			—	—
Change in value of Series B Warrants	—	—			—		(271,416		)	—	—
Change in value of Series C Warrants	—	—			—		—			—	(376,947		)
Balance at December 31, 2016	2,425,605	$	194,048		—		$	—		590,415	$	85,490