Significant Accounting Policies - Additional Information (Details) - USD ($)		3 Months Ended												12 Months Ended			36 Months Ended
	Jan. 01, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Impairment losses on short-term investments																	$ 0
Inventory write-offs														$ 684,000	$ 489,000	$ 774,000
Impairment of long-lived assets																	0
Increase (decrease) in trade receivables														4,151,000	23,228,000	6,339,000
Net revenues		$ 69,674,000	$ 64,756,000	$ 61,514,000	$ 52,125,000	$ 53,661,000	$ 50,109,000	$ 38,376,000	$ 34,880,000	$ 30,242,000	$ 21,674,000	$ 17,919,000	$ 13,053,000	248,069,000	177,026,000	82,888,000
Increase (decrease) in net loss		$ (15,631,000)	$ (11,694,000)	$ (15,510,000)	$ (20,724,000)	$ (10,945,000)	$ (11,498,000)	$ (21,174,000)	$ (18,045,000)	$ (22,168,000)	$ (33,628,000)	$ (40,612,000)	$ (35,437,000)	$ (63,559,000)	$ (61,662,000)	$ (131,845,000)
Increase (decrease) in basic and diluted net loss per ordinary share		$ (0.17)	$ (0.13)	$ (0.17)	$ (0.23)	$ (0.12)	$ (0.13)	$ (0.24)	$ (0.21)	$ (0.26)	$ (0.39)	$ (0.48)	$ (0.42)	$ (0.69)	$ (0.70)	$ (1.54)
Increase in other payables and accrued expenses														$ 4,210,000	$ 14,460,000	$ 6,647,000
Indirect taxes														1,698,000	1,239,000	972,000
Cost related to charitable care														2,762,000	1,483,000	1,675,000
Pension expense														882,000	1,036,000	529,000
Severance costs														526,000	506,000	430,000
Sales Revenue Net | Customer One | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Net revenues														$ 22,959,000	$ 15,479,000	$ 10,393,000
Concentration risk percentage														9.00%	9.00%	13.00%
Restricted Share Unit
Significant Accounting Policies [Line Items]
Stock awards granted, vesting period														3 years
Option
Significant Accounting Policies [Line Items]
Stock awards granted, vesting period														4 years
Expected dividend yield														0.00%	0.00%	0.00%
Shipping and Handling
Significant Accounting Policies [Line Items]
Direct costs included in sales and marketing costs														$ 2,936,000	$ 5,322,000	$ 3,389,000
Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Increase (decrease) in trade receivables														(6,288,000)
Cumulative deficit effect adjustment resulting from ASU adoption		$ (6,517,000)												(6,517,000)			$ (6,517,000)
Increase (decrease) in net loss		$ 4,136,000												$ 8,679,000
Increase (decrease) in basic and diluted net loss per ordinary share		$ 0.04												$ 0.09
Increase in other payables and accrued expenses														$ 1,052,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Significant Accounting Policies [Line Items]
Increase (decrease) in trade receivables	$ 2,807,000
Increase in deferred revenue	645,000
Cumulative deficit effect adjustment resulting from ASU adoption	$ (2,162,000)
Net revenues		$ (4,054,000)												$ (8,683,000)
Accounting Standards Update 2014-09 | First Generation Optune System Field Equipment
Significant Accounting Policies [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. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. The Company has agreements with many payers that define explicit discounts off the gross transaction price. In addition to the explicit discounts negotiated with each payer, the Company expects to receive, in aggregate for a given portfolio, less than the gross revenue net of explicit discounts. ASC 606 requires that the Company recognize this variable consideration as an implicit discount in the billing period. The implicit discount includes both an estimate of claims that will pay at an amount less than billed and an estimate of claims that will not pay within a given time horizon. The implicit discount adjustments to the transaction price are due to concessions, not collectability concerns driven by payer credit risk.
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 a combined 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.
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Cumulative deficit effect adjustment resulting from ASU adoption										$ 670,000						670,000
Accounting Standards Update 2016-02 | Subsequent Event
Significant Accounting Policies [Line Items]
Operating leases right-of-use assets																		$ 15,733,000
Operating lease liabilities																		$ 15,733,000
Field Equipment Under Operating Leases
Significant Accounting Policies [Line Items]
Equipment write-downs included in cost of revenue														$ 350,000	$ 195,000	$ 6,436,000
Field Equipment Under Operating Leases | Minimum
Significant Accounting Policies [Line Items]
Property and equipment useful life														18 months
Field Equipment Under Operating Leases | Maximum
Significant Accounting Policies [Line Items]
Property and equipment useful life														36 months