Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies [Abstract]

Fair Value Measurements by Level for Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table summarizes fair value measurements by level at December 31, 2017 for assets and liabilities measured at fair value on a recurring basis:

(In thousands)	Level I		Level II		Level III			Total
Cash equivalents	$	35,834	$	—	$	—		$	35,834
Warrant liabilities		—		—		(527	)		(527	)

The following table summarizes fair value measurements by level at December 31, 2016 for assets and liabilities measured at fair value on a recurring basis:

(In thousands)	Level I		Level II		Level III			Total
Cash equivalents	$	56,276	$	—	$	—		$	56,276
Warrant liabilities		—		—		(3,789	)		(3,789	)

Changes in Carrying Amounts of Warrant Liabilities

The changes in carrying amounts of the warrant liability for the years ended December 31, 2017 and 2016 were as follows:

(In thousands)	2017			2016
Beginning balance	$	3,789		$	693
Issued		—			6,933
Exercised		(1,895	)		(9	)
Net changes in valuation		(1,367	)		(3,828	)
Ending balance	$	527		$	3,789