Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	Apr. 24, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Trading Symbol	KRTX
Entity Registrant Name	Karuna Therapeutics, Inc.
Entity Central Index Key	0001771917
Current Fiscal Year End Date	--12-31
Entity File Number	001-38958
Entity Tax Identification Number	27-0605902
Entity Address, Address Line One	99 High Street
Entity Address, Address Line Two	26th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02110
City Area Code	857
Local Phone Number	449-2244
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		37,443,954
Entity Shell Company	false
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE