Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 03, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Common stock purchase limit (in shares)	39,149,000		39,149,000		6,006,667	37,026,000
Price per share (in usd per share)					$ 1.00
Change in fair value of Warrant liability	$ 599	$ 0	$ 1,102	$ 0