| Document and Entity Information | Mar. 11, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | NATIONAL FUEL GAS CO |
| Amendment Flag | false |
| Entity Central Index Key | 0000070145 |
| Document Type | 8-K |
| Document Period End Date | Mar. 11, 2021 |
| Entity Incorporation State Country Code | NJ |
| Entity File Number | 1-3880 |
| Entity Tax Identification Number | 13-1086010 |
| Entity Address, Address Line One | 6363 Main Street |
| Entity Address, City or Town | Williamsville |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 14221 |
| City Area Code | (716) |
| Local Phone Number | 857-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $1.00 per share |
| Trading Symbol | NFG |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
