Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	EIDX
Entity Registrant Name	EIDOS THERAPEUTICS, INC.
Entity Central Index Key	0001731831
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		38,571,002
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity File Number	001-38533
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3733671
Entity Address, Address Line One	101 Montgomery Street
Entity Address, Address Line Two	Suite 2000
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94104
City Area Code	415
Local Phone Number	887-1471
Document Quarterly Report	true
Document Transition Report	false