XML 13 R1.htm IDEA: XBRL DOCUMENT v3.22.1
Cover Page - shares
3 Months Ended
Mar. 31, 2022
Apr. 21, 2022
Cover page.    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2022  
Document Transition Report false  
Entity File Number 1-13105  
Entity Registrant Name Arch Resources, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 43-0921172  
Entity Address, Address Line One One CityPlace Drive  
Entity Address, Address Line Two Suite 300  
Entity Address, City or Town St. Louis  
Entity Address, State or Province MO  
Entity Address, Postal Zip Code 63141  
City Area Code 314  
Local Phone Number 994-2700  
Title of 12(b) Security Common stock, $.01 par value  
Trading Symbol ARCH  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business Company false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding (in shares)   15,477,360
Amendment Flag false  
Entity Central Index Key 0001037676  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2022  
Document Fiscal Period Focus Q1