Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Organization and Basis of Presentation [Line Items]
Increase (decrease) in trade receivables	$ 3,599	$ 2,064	$ 5,271	$ 7,550	$ 23,228
Decrease in net revenue	61,514	38,376	113,639	73,256	177,026
Net loss	$ (15,510)	$ (21,174)	$ (36,234)	$ (39,219)	$ (61,662)
Decrease in basic and diluted net loss per ordinary share	$ (0.17)	$ (0.24)	$ (0.40)	$ (0.45)	$ (0.70)
Increase in other payables and accrued expenses	$ (528)	$ 4,888	$ (8,828)	$ 3,478	$ 14,460
Accounting Standards Update 2014-09 [Member]
Organization and Basis of Presentation [Line Items]
Increase (decrease) in trade receivables			(2,760)		2,807
Increase in deferred revenue					645
Cumulative deficit effect adjustment resulting from ASU 2014-09 adoption	(3,209)		(3,209)		$ (2,162)
Net loss	$ (2,035)		$ (5,371)
Decrease in basic and diluted net loss per ordinary share	$ (0.02)		$ (0.06)
Increase in other payables and accrued expenses			$ 521
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Organization and Basis of Presentation [Line Items]
Decrease in net revenue	$ (1,993)		$ (5,531)
Accounting Standards Update 2014-09 [Member] | First Generation Optune System Field Equipment [Member]
Organization and Basis of Presentation [Line Items]
Identify the contract with patient			Identify the contract with a patient. A contract with a patient exists when (i) the Company enters into an enforceable contract with a patient that defines each party’s rights regarding delivery of and payment for Optune, (ii) the contract has commercial substance and (iii) the Company determines that collection of substantially all consideration for Optune is probable based on the payer’s intent and ability to pay the promised consideration. The evidence of a contract generally consists of a prescription, a patient service agreement and the verification of the assigned payer for the contract and intention to collect.
Identify the performance obligations in the contract, description			Optune contracts include the lease of the device, the supply obligation of disposable transducer arrays and technical support for the term of treatment. To the extent a contract includes multiple promised products and/or services, the Company must apply judgment to determine whether those products and/or services are capable of being distinct in the context of the contract. If these criteria are not met the promised products and/or services are accounted for as a combined performance obligation. In the Company’s case, Optune’s device, support, and disposables are provided as one inseparable package of monthly treatment for a single monthly fee
Determine the transaction price, description			The transaction price is determined based on the consideration to which the Company will be entitled in exchange for providing Optune to the patient.
Allocate the transaction price to performance obligations in the contract, description			If a contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. As discussed above, there is one performance obligation under the Company’s contracts and, therefore, the monthly transaction price determined for the performance obligation will be recognized over time ratably over the monthly term of the treatment.
Recognize revenue when or as the company satisfies a performance obligation, description			The Company satisfies performance obligations over time as discussed above. Revenue is recognized at the time the related performance obligation is satisfied by transferring a promised service to a patient. The patient consumes the benefits of Optune treatment on a daily basis over the monthly term. As this criterion is met, the revenues will be recognized over the monthly term.