Cover - shares	3 Months Ended
	Mar. 31, 2021	Apr. 23, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
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
City Area Code	44 (0) 15
Local Phone Number	3475 6700
Title of 12(b) Security	Ordinary Shares, no par value
Trading Symbol	NVCR
Security Exchange Name	NASDAQ
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 Common Stock, Shares Outstanding		103,413,367
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001645113
Current Fiscal Year End Date	--12-31