Commitments and Contingencies - Operating Leases - (Details) - USD ($) $ in Thousands			1 Months Ended		3 Months Ended
	May 14, 2021	Feb. 01, 2021	Sep. 30, 2019	May 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Commitments and Contingencies
Right-of-use assets and other					$ 123		$ 130
Lease asset liability					89
Operating lease, liability current					24		24
Operating lease, liability noncurrent					$ 65
Korea
Commitments and Contingencies
Term of contract				5 years
Option to renew				true
Renewal term				5 years
Operating lease discount rate					10.00%
Weighted average remaining lease term					3 years 3 months
Non-cash expense related to Korea lease						$ 5
Operating lease cash payments					$ 8
Head Quarters in Boston Lease
Commitments and Contingencies
Term of contract	6 months	6 months	1 year
Monthly rental cost	$ 3	$ 3	$ 21
Rent concessions granted by the landlord	$ 2	$ 1	$ 32
Lease expense					115	35
Termination fee						$ 83
Right-of-use assets and other					0		0
Lease asset liability					$ 0		$ 0