| Cover Page | Oct. 30, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Oct. 30, 2019 |
| Entity Registrant Name | WARRIOR MET COAL, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38061 |
| Entity Tax Identification Number | 81-0706839 |
| Entity Address, Address Line One | 16243 Highway 216 |
| Entity Address, City or Town | Brookwood |
| Entity Address, State or Province | AL |
| Entity Address, Postal Zip Code | 35444 |
| City Area Code | 205 |
| Local Phone Number | 554-6150 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $.01 per share |
| Trading Symbol | HCC |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001691303 |
| Amendment Flag | false |
