Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary of valuation of the Company's investments and financial instruments that are measured at fair value on a recurring basis

The following table summarizes the valuation of the Company’s financial instruments that are measured at fair value on a recurring basis: 

	December 31, 2017								December 31, 2016
	Fair value measurement category								Fair value measurement category
(In thousands)	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Liabilities:
Warrant liabilities	$	1,014	$	—	$	1,014	$	—	$	757	$	—	$	757	$	—

Summary of change in estimated fair values of warrant liabilities

The following table summarizes the change in the estimated fair value of the Company’s warrant liabilities: 

Warrant Liabilities (In thousands)
Balance at December 31, 2015	$	757
Change in fair value	—
Balance at December 31, 2016	757
Change in fair value	257
Balance at December 31, 2017	$	1,014