Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 05, 2021	Jun. 30, 2020
Cover [Abstract]
Title of 12(b) Security	Common stock, $0.01 par value per share
Entity Incorporation, State or Country Code	DE
Document Transition Report	false
Document Quarterly Report	true
Entity Tax Identification Number	42-0991521
Entity Address, Address Line One	2140 Lake Park Blvd
Entity Address, City or Town	Richardson
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75080
City Area Code	972
Trading Symbol	LII
Security Exchange Name	NYSE
Local Phone Number	497-5000
Entity Registrant Name	LENNOX INTERNATIONAL INC.
Entity Central Index Key	0001069202
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity File Number	001-15149
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 8.9
Entity Common Stock, Shares Outstanding		37,733,565
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCEPortions of the registrant’s 2020 Definitive Proxy Statement to be filed with the Securities and Exchange Commission in connection with the registrant’s 2020 Annual Meeting of Stockholders to be held on May 20, 2021 are incorporated by reference into Part III of this report.
ICFR Auditor Attestation Flag	true