| Document and Entity Information | May 22, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | Apergy Corp |
| Amendment Flag | false |
| Entity Central Index Key | 0001723089 |
| Document Type | 8-K |
| Document Period End Date | May 22, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38441 |
| Entity Tax Identification Number | 82-3066826 |
| Entity Address, Address Line One | 2445 Technology Forest Blvd |
| Entity Address, Address Line Two | Building 4 |
| Entity Address, Address Line Three | 12th Floor |
| Entity Address, City or Town | The Woodlands |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77381 |
| City Area Code | (281) |
| Local Phone Number | 403-5772 |
| Written Communications | true |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock $0.01 Par Value |
| Trading Symbol | APY |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
