Cover Page - shares	3 Months Ended
	Mar. 31, 2020	Apr. 24, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-38061
Entity Registrant Name	Warrior Met Coal, Inc.
Entity Incorporation, State or Country Code	DE
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		51,167,697
Entity Central Index key	0001691303
Document Fiscal Year Focus	2020
Amendment Flag	false
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	HCC
Security Exchange Name	NYSE
Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Rights to Purchase Series A Junior Participating Preferred Stock, par value $0.01 per share
Security Exchange Name	NYSE
No Trading Symbol Flag	true