Patent License Agreement (Details) $ in Thousands, £ in Millions			1 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2019 GBP (£)	Dec. 31, 2018 USD ($)	Aug. 31, 2017 USD ($)	Jan. 31, 2017 USD ($) shares	Jan. 31, 2017 GBP (£) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Finite-Lived Intangible Assets [Line Items]
One-time upfront payment for finite-lived intangible asset							$ 2,500	$ 0	$ 0
Capitalized license fees		$ 7,800				$ 7,800	6,890	7,800
Patent Licensing Agreement
Finite-Lived Intangible Assets [Line Items]
One-time upfront payment for finite-lived intangible asset				$ 1,100	£ 1.0
Milestone payment			$ 1,200		£ 1.0
Future royalty payments | £	£ 13.4
Capitalized license fees		$ 7,800		$ 6,300		7,800	6,900	$ 7,800
Intangible assets, useful life	7 years	8 years
Amortization of intangible assets						$ 900	$ 1,000
Series D Convertible Preferred Stock | Patent Licensing Agreement
Finite-Lived Intangible Assets [Line Items]
Stock issued during period for purchase of asset, shares | shares				141,774	141,774
Fair value of stock issued for purchase of license agreement				$ 1,100
Discount Rate
Finite-Lived Intangible Assets [Line Items]
Debt security, measurement input				0.15