Revenue Recognition, Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Treatment Equipment [Abstract]
Lease term	36 months
Contract with Customer, Liability [Abstract]
Short-term contract liabilities	$ 79
Long-term contract liabilities	2
Change in Contract with Customer, Liability [Abstract]
Contract liabilities recognized as revenue	34	$ 57
Co-pay reimbursements recorded as reduction of revenue	$ (157)	$ (168)
Minimum [Member]
Treatment Equipment [Abstract]
Notice period to cancel contract agreement	30 days
Maximum [Member]
Treatment Equipment [Abstract]
Notice period to cancel contract agreement	60 days
South Korea [Member]
Treatment Equipment [Abstract]
Lease term	48 months