LEASES - Lease cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Leases
Total operating lease expense	$ 1,150	$ 926
Total amortization of right-of-use asset	19	10
Interest expense and other	5	2
Total finance lease expense	24	12
Costs of revenue - devices and supplies
Leases
Total operating lease expense	121	142
Total amortization of right-of-use asset	2
Sales and marketing expense
Leases
Total operating lease expense	170	114
Total amortization of right-of-use asset	4
General, and administrative
Leases
Total operating lease expense	859	670
Total amortization of right-of-use asset	$ 13	$ 10