Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Mar. 06, 2020	Jun. 28, 2019
Document And Entity Information Abstract
Entity Registrant Name	Entasis Therapeutics Holdings Inc.
Entity Central Index Key	0001724344
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 84.7
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		13,291,563
Entity Shell Company	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY