| Document and Entity Information | Aug. 09, 2023 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001691303 |
| Document Type | 8-K |
| Document Period End Date | Aug. 09, 2023 |
| Entity Registrant Name | WARRIOR MET COAL, INC. |
| Entity Incorporation State 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 |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | HCC |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Rights to Purchase Series A Junior Participating Preferred Stock, par value $0.01 per share |
| Trading Symbol | — |
| Security Exchange Name | NYSE |
