Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 23, 2021	Jun. 30, 2020
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Entity File Number	000-30941
Entity Registrant Name	AXCELIS TECHNOLOGIES INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	34-1818596
Entity Address, Address Line One	108 Cherry Hill Drive
Entity Address, City or Town	Beverly
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01915
City Area Code	978
Local Phone Number	787-4000
Title of 12(b) Security	Common Stock, $.001 par value
Trading Symbol	ACLS
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 Common Stock, Shares Outstanding		33,732,089
Entity Public Float			$ 914,478,137
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001113232
Amendment Flag	false
ICFR Auditor Attestation Flag	true