Revenue Recognition, Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Treatment Equipment [Abstract]
Lease term	36 months		36 months
Contract with Customer, Liability [Abstract]
Short-term contract liabilities	$ 1,148		$ 1,148
Long-term contract liabilities	401		401
Change in Contract with Customer, Liability [Abstract]
Contract liabilities recognized as revenue	19	$ 52	73	$ 162
Co-pay reimbursements recorded as reduction of revenue	$ (199)	$ (160)	$ (542)	$ (414)
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		48 months