Stock Purchase Warrants - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Dec. 27, 2017	Dec. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 06, 2017
Stock Purchase Warrants
Proceeds from issuance of warrants			$ 0	$ 0	$ 207
ICT
Stock Purchase Warrants
Initial license agreement payment		$ 5,200
ICT | Potential Payment
Stock Purchase Warrants
Other commitment		1,200			$ 1,200
Common Stock
Stock Purchase Warrants
Conversion of preferred stock for common stock (Note 9) (in shares)					1,094,000
Exercise of warrants resulting in the issuance of common stock (in shares)			20,000	681,000	817,000
December 2017 Warrants
Stock Purchase Warrants
Exercise price (in dollars per share)			$ 4.27
Warrants outstanding (in shares)			0
December 2017 Warrants | Common Stock
Stock Purchase Warrants
Conversion of preferred stock for common stock (Note 9) (in shares)			19,808
December 21, 2017 Warrants | ICT
Stock Purchase Warrants
Exercise price (in dollars per share)						$ 0.01
Proceeds from issuance of warrants		$ 4,000
Total shares issuable on exercise		818,424
Share price (in dollars per share)						$ 4.90
Exercise of warrants resulting in the issuance of common stock (in shares)	816,850
Warrants outstanding (in shares)			0