Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 31, 2020
Cover [Abstract]
Document Type	10-Q/A
Amendment Flag	true
Amendment Description	This Amendment No. 1 (the "Amendment") to the Quarterly Report on Form 10-Q of AlloVir, Inc. (the "Company") for the quarter ended June 30, 2020, originally filed with the Securities and Exchange Commission on September 2, 2020 (the "Original Form 10-Q"), is being filed solely to correct an administrative error in the number of outstanding shares of the Company's common stock, as of August 31, 2020, listed on the cover page. The cover page of this Amendment correctly states that the number of shares of common stock outstanding on August 31, 2020 was 65,106,873. No other parts of the Original Form 10-Q presented incorrect share information.This Amendment is limited in scope to the correction described above and does not amend, update, or change any other items or disclosures contained in the Original Form 10-Q. Accordingly, all other items that remain unaffected are omitted in this filing. Except as described in the preceding paragraph, we do not purport by this Amendment to update any of the information contained in the Original Form 10-Q, which continues to speak as of the original filing date of the Original Form 10-Q.
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	ALVR
Entity Registrant Name	ALLOVIR, INC.
Entity Central Index Key	0001754068
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		65,106,873
Security12b Title	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39409
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	83-1971007
Entity Address Address Line1	139 Main Street
Entity Address, Address Line Two	Suite 500
Entity Address City Or Town	Cambridge
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02142
City Area Code	617
Local Phone Number	433-2605
Document Quarterly Report	true
Document Transition Report	false