Intangible Assets - Finite-lived intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross	$ 5,224	$ 5,224	$ 5,224
Accumulated Amortization	(4,136)	(4,433)	(4,136)
Foreign Exchange Rate Changes	(174)	(174)	(174)
Total	914	617	914
Amortization expense	74	297		$ 326
Patents
Finite-Lived Intangible Assets [Line Items]
Gross	2,963	2,963	2,963
Accumulated Amortization	(2,049)	(2,346)	(2,049)
Foreign Exchange Rate Changes	0	0	0
Total	914	$ 617	$ 914
Estimated Useful Life (in years)		10 years	10 years
Developed Technology - 150V
Finite-Lived Intangible Assets [Line Items]
Gross	560	$ 560	$ 560
Accumulated Amortization	(517)	(517)	(517)
Foreign Exchange Rate Changes	(43)	(43)	(43)
Total	0	$ 0	$ 0
Estimated Useful Life (in years)		6 years	6 years
Developed Technology - 600V
Finite-Lived Intangible Assets [Line Items]
Gross	1,701	$ 1,701	$ 1,701
Accumulated Amortization	(1,570)	(1,570)	(1,570)
Foreign Exchange Rate Changes	(131)	(131)	(131)
Total	$ 0	$ 0	$ 0
Estimated Useful Life (in years)		6 years	6 years