Document and Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2021	Jul. 31, 2021	Dec. 31, 2020
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-31298
Entity Registrant Name	LANNETT COMPANY, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-0787699
Entity Address, Address Line One	1150 Northbrook Drive, Suite 155
Entity Address, City or Town	Trevose
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19053
City Area Code	215
Local Phone Number	333-9000
Title of 12(b) Security	Common Stock
Trading Symbol	LCI
Security Exchange Name	NYSE
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 Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 214,124,709
Entity Common Stock, Shares Outstanding		42,276,052
Entity Central Index Key	0000057725
Current Fiscal Year End Date	--06-30
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false