Cover - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 19, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-37565
Entity Registrant Name	NovoCure Limited
Entity Incorporation, State or Country Code	Y9
Entity Tax Identification Number	98-1057807
Entity Address, Address Line One	No. 4 The Forum
Entity Address, Address Line Two	Grenville Street
Entity Address, City or Town	St. Helier
Entity Address, Country	JE
Entity Address, Postal Zip Code	JE2 4UF
Country Region	+44
City Area Code	(0) 15
Local Phone Number	3475 6700
Title of 12(b) Security	Ordinary shares, no par value per share
Trading Symbol	NVCR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 3,943,182,013
Entity Common Stock, Shares Outstanding		99,640,549
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for its 2020 annual meeting of shareholders are incorporated by reference into Items 10, 11, 12, 13, and 14 of Part III of this Form 10-K.  Such definitive proxy statement will be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2019.
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001645113
Current Fiscal Year End Date	--12-31