Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Period End Date	Dec. 31, 2019
Document Fiscal Period Focus	FY
Entity Registrant Name	MADRIGAL PHARMACEUTICALS, INC.
Entity Central Index Key	0001157601
Entity File Number	001-33277
Current Fiscal Year End Date	--12-31
Entity Tax Identification Number	04-3508648
Entity Incorporation, State or Country Code	DE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 884,202,105
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		15,429,154
City Area Code	267
Local Phone Number	824-2827
Trading Symbol	MDGL
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Entity Address, Address Line One	Four Tower Bridge
Entity Address, Address Line Two	200 Barr Harbor Drive, Suite 200
Entity Address, City or Town	West Conshohocken
Entity Address, Postal Zip Code	19428
Entity Address, State or Province	PA