| Document and Entity Information Document | Feb. 01, 2024 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 01, 2024 |
| Entity Registrant Name | ILLINOIS TOOL WORKS INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-4797 |
| Entity Tax Identification Number | 36-1258310 |
| Entity Address, Address Line One | 155 Harlem Avenue |
| Entity Address, City or Town | Glenview |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60025 |
| City Area Code | 847 |
| Local Phone Number | 724-7500 |
| 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 | 0000049826 |
| Amendment Flag | false |
| NEW YORK STOCK EXCHANGE, INC. | Common Stock | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | ITW |
| Security Exchange Name | NYSE |
| NEW YORK STOCK EXCHANGE, INC. | 0.250% Euro Notes due 2024 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.250% Euro Notes due 2024 |
| Trading Symbol | ITW24A |
| Security Exchange Name | NYSE |
| NEW YORK STOCK EXCHANGE, INC. | 0.625% Euro Notes due 2027 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 0.625% Euro Notes due 2027 |
| Trading Symbol | ITW27 |
| Security Exchange Name | NYSE |
| NEW YORK STOCK EXCHANGE, INC. | 2.125% Euro Notes due 2030 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 2.125% Euro Notes due 2030 |
| Trading Symbol | ITW30 |
| Security Exchange Name | NYSE |
| NEW YORK STOCK EXCHANGE, INC. | 1.00% Euro Notes due 2031 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 1.00% Euro Notes due 2031 |
| Trading Symbol | ITW31 |
| Security Exchange Name | NYSE |
| NEW YORK STOCK EXCHANGE, INC. | 3.00% Euro Notes due 2034 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 3.00% Euro Notes due 2034 |
| Trading Symbol | ITW34 |
| Security Exchange Name | NYSE |
