Commitments and Contingencies - Operating Leases - (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Sep. 30, 2019	May 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Commitments and Contingencies
Right-of-use assets and other			$ 143		$ 150
Operating lease, liability current			22		$ 22
Operating lease, liability noncurrent			89
Operating lease cash payments			$ 5
Korea
Commitments and Contingencies
Term of contract		5 years
Option to renew		true
Renewal term		5 years
Right-of-use assets and other	$ 126
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherCurrentLiabilitiesMember
Operating lease, liability current	$ 20
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherNoncurrentLiabilitiesMember
Operating lease, liability noncurrent	$ 106
Operating lease discount rate			10.00%
Weighted average remaining lease term			4 years 3 months
Non-cash expense related to Korea lease			$ 8	$ 0
Operating lease cash payments			8	0
Head Quarters in Boston Lease
Commitments and Contingencies
Term of contract	1 year
Monthly rental cost	$ 21
Rent concessions granted by the landlord	$ 32
Lease expense			115	$ 26
Termination fee			$ 83