Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value

A summary of the assets and liabilities carried at fair value in accordance with the hierarchy defined above is as follows:

	Fair Value Measurements Using
	Total Carrying Value		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
December 31, 2015
Assets:
Cash equivalents	$	23,154	$	9,208	$	13,946	$	—
Short-term investments		63,310		—		63,310		—
Total assets	$	86,464	$	9,208	$	77,256	$	—
Liabilities:
Derivative liability	$	133	$	—	$	—	$	133
Common stock warrant liability		2,848		—		—		2,848
Total liabilities	$	2,981	$	—	$	—	$	2,981
March 31, 2016
Assets:
Cash equivalents	$	21,890	$	18,354	$	3,536	$	—
Short-term investments		110,483		—		110,483		—
Total assets	$	132,373	$	18,354	$	114,019	$	—

Summary of Available-for-Sale Securities

The following table summarizes the available-for-sale securities:

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(In thousands)
December 31, 2015
Commercial paper	$	28,980	$	48	$	—		$	29,028
Corporate bonds		34,302		—		(20	)		34,282
	$	63,282	$	48	$	(20	)	$	63,310
March 31, 2016
Commercial paper	$	66,152	$	221	$	—		$	66,373
Corporate bonds		44,103		8		(1	)		44,110
	$	110,255	$	229	$	(1	)	$	110,483

Summary of Changes in Fair Value of Common Stock Warrant Liability and Derivative Liability Inputs

A roll-forward of the recurring fair value measurements of the common stock warrant liability and the derivative liability categorized with Level 3 inputs is as follows:

	Common Stock Warrant Liability			Derivative Liability
	(In thousands)
Balance — December 31, 2014	$	693		$	126
Change in fair value		132			4
Balance—March 31, 2015	$	825		$	130
	Common Stock Warrant Liability			Derivative Liability
	(In thousands)
Balance — December 31, 2015	$	2,848		$	133
Change in fair value		1,703			17
Reclassification		(4,551	)		(150	)
Balance—March 31, 2016	$	—		$	—