Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 11, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2019
Entity File Number	001-15149
Entity Registrant Name	LENNOX INTERNATIONAL INC
Entity Incorporation, State or Country Code	DE
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
Local Phone Number	497-5000
Title of 12(b) Security	Common stock, $0.01 par value per share
Trading Symbol	LII
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		38,531,575
Entity Central Index Key	0001069202
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31