| **Cover Page - shares**                     | 3 Months Ended                           |             |
|---------------------------------------------|------------------------------------------|-------------|
||
| **Document Information [Line Items]**       |                                     |        |
| Document Type                               | 10-Q                                     |        |
| Document Quarterly Report                   | true                                     |        |
| Document Period End Date                    | Mar. 31,  2024                           |        |
| Document Transition Report                  | false                                    |        |
| Entity File Number                          | 1-475                                    |        |
| Entity Registrant Name                      | A. O. Smith Corporation                  |        |
| Entity Incorporation, State or Country Code | DE                                       |        |
| Entity Tax Identification Number            | 39-0619790                               |        |
| Entity Address, Address Line One            | 11270 West Park Place                    |        |
| Entity Address, City or Town                | Milwaukee                                |        |
| Entity Address, State or Province           | WI                                       |        |
| Entity Address, Postal Zip Code             | 53224-9508                               |        |
| City Area Code                              | 414                                      |        |
| Local Phone Number                          | 359-4000                                 |        |
| Title of 12(b) Security                     | Common Stock (par value $1.00 per share) |        |
| Trading Symbol                              | AOS                                      |        |
| 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                                    |        |
| Amendment Flag                              | false                                    |        |
| Entity Central Index Key                    | 0000091142                               |        |
| Document Fiscal Period Focus                | Q1                                       |        |
| Current Fiscal Year End Date                | --12-31                                  |        |
| Document Fiscal Year Focus                  | 2024                                     |        |
| Class A Common Stock                        |                                     |        |
| **Document Information [Line Items]**       |                                     |        |
| Entity Common Stock, Shares Outstanding     |                                     | 25,886,364  |
| Common Stock                                |                                     |        |
| **Document Information [Line Items]**       |                                     |        |
| Entity Common Stock, Shares Outstanding     |                                     | 120,783,753 |

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