Field Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Field Equipment [Line Items]
Depreciation	$ 1,967	$ 1,968	$ 1,673
Impairment of field equipment			6,412
Field equipment
Field Equipment [Line Items]
Depreciation	5,553	4,483	3,248
Field Equipment Under Operating Leases
Field Equipment [Line Items]
Impairment of field equipment	$ 350	$ 195	6,436
First Generation Optune System Field Equipment | Cost of Revenues
Field Equipment [Line Items]
Impairment of field equipment			6,412
First Generation Optune System Field Equipment | Cost of Revenues | Finished Goods
Field Equipment [Line Items]
Impairment of field equipment			4,830
First Generation Optune System Field Equipment | Cost of Revenues | Production Stage Goods
Field Equipment [Line Items]
Impairment of field equipment			$ 1,582