| Document and Entity Information | Mar. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 12, 2021 |
| Entity Registrant Name | LOEWS CORPORATION |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-6541 |
| Entity Tax Identification Number | 13-2646102 |
| Entity Address, Address Line One | 667 Madison Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10065-8087 |
| City Area Code | 212 |
| Local Phone Number | 521-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000060086 |
| Title of 12(b) Security | Common stock, $0.01 par value |
| Trading Symbol | L |
| Security Exchange Name | NYSE |
