| Cover | Apr. 28, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 28, 2021 |
| Entity Registrant Name | ALPHA METALLURGICAL RESOURCES, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38735 |
| Entity Tax Identification Number | 81-3015061 |
| Entity Address, Address Line One | 340 Martin Luther King Jr. Blvd. |
| Entity Address, City or Town | Bristol |
| Entity Address, State or Province | TN |
| Entity Address, Postal Zip Code | 37620 |
| City Area Code | 423 |
| Local Phone Number | 573-0300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | AMR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001704715 |
