| Document and Entity Information Document and Entity Information | Feb. 04, 2020 |
| Cover page. | |
| Entity Central Index Key | 0001069202 |
| Entity Incorporation, State or Country Code | DE |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | LII |
| Security Exchange Name | NYSE |
| Pre-commencement Issuer Tender Offer | false |
| Pre-commencement Tender Offer | false |
| Soliciting Material | false |
| Written Communications | false |
| Document Type | 8-K |
| Document Period End Date | Feb. 4, 2020 |
| Entity Registrant Name | LENNOX INTERNATIONAL INC |
| 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 |
| Entity File Number | 001-15149 |
| Entity Tax Identification Number | 42-0991521 |
| City Area Code | 972 |
| Local Phone Number | 497-5000 |
| Amendment Flag | false |
| Entity Emerging Growth Company | false |
