Intangible Assets - Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 5,224		$ 5,224	$ 5,224
Finite-Lived Intangible Assets, Accumulated Amortization	(4,136)		(4,214)	(3,773)
Finite Lived Intangible Assets, Accumulated Change in Foreign Exchange Rate	(174)		(22)	(138)
Total	914		988	1,313
Amortization expense	74	$ 103	326	653
Patents
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,963		2,963	2,963
Finite-Lived Intangible Assets, Accumulated Amortization	(2,049)		(1,975)	(1,679)
Finite Lived Intangible Assets, Accumulated Change in Foreign Exchange Rate	0		0	0
Total	$ 914		$ 988	$ 1,284
Intangible assets, estimated useful life	10 years		10 years	10 years
Developed Technology - 150V
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 560		$ 560	$ 560
Finite-Lived Intangible Assets, Accumulated Amortization	(517)		(555)	(519)
Finite Lived Intangible Assets, Accumulated Change in Foreign Exchange Rate	(43)		(5)	(34)
Total	$ 0		$ 0	$ 7
Intangible assets, estimated useful life	6 years		6 years	6 years
Developed Technology - 600V
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 1,701		$ 1,701	$ 1,701
Finite-Lived Intangible Assets, Accumulated Amortization	(1,570)		(1,684)	(1,575)
Finite Lived Intangible Assets, Accumulated Change in Foreign Exchange Rate	(131)		(17)	(104)
Total	$ 0		$ 0	$ 22
Intangible assets, estimated useful life	6 years		6 years	6 years