v3.26.3
Long-Term Debt - Narrative (Details) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Mar. 27, 2025
Jan. 13, 2025
Jan. 31, 2025
Sep. 30, 2026
Jun. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Debt Instrument [Line Items]                          
Segment assets       $ 6,059,843,000     $ 6,195,888,000     $ 6,059,843,000 $ 6,195,888,000 $ 6,130,053,000  
Net income attributable to the SPVs       8,998,000 $ 126,467,000 $ 21,044,000 31,598,000 $ (36,556,000) $ (69,277,000) 156,509,000 (74,235,000)    
Loss on extinguishment of debt       0     0     0 11,680,000    
Arch Resources, Inc                          
Debt Instrument [Line Items]                          
Purchase price consideration   $ 98,075,000                      
Accounts Receivable Securitization Facility | Line of Credit                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity       250,000,000           $ 250,000,000      
Reduced annual rate                   0.10%      
Letters of credit outstanding       187,739,000           $ 187,739,000   158,282,000  
Unused borrowing capacity       $ 62,261,000           62,261,000   $ 26,840,000  
Proceeds from lines of credit                   0 0    
Repayments of lines of credit                   $ 0 0    
PEDFA Solid Waste Disposal Facility Revenue Bonds at 5.45%                          
Debt Instrument [Line Items]                          
Letters of credit outstanding $ 75,000,000                        
Debt instrument, face amount $ 97,560,000                        
Debt instrument, interest rate, stated percentage 5.45%     5.45%           5.45%   5.45%  
Debt instrument, term 10 years                        
MEDCO Port Facilities Refunding Revenue Bonds at 5.00%                          
Debt Instrument [Line Items]                          
Letters of credit outstanding $ 102,865,000                        
Debt instrument, face amount $ 102,865,000                        
Debt instrument, interest rate, stated percentage 5.00%     5.00%           5.00%   5.00%  
Debt instrument, term 10 years                        
WVEDA Solid Waste Disposal Facility Revenue Bonds at 5.45%                          
Debt Instrument [Line Items]                          
Debt instrument, face amount $ 106,355,000                        
Debt instrument, interest rate, stated percentage 5.45%     5.45%           5.45%   5.45%  
Debt instrument, term 10 years                        
Non-Guarantor Subsidiaries                          
Debt Instrument [Line Items]                          
Segment assets       $ 392,368,000           $ 392,368,000   $ 350,156,000  
Trade receivables       390,223,000           390,223,000   347,093,000  
Net income attributable to the SPVs       15,000     $ 3,776,000     2,521,000 $ 8,408,000    
Revolving Credit Facility                          
Debt Instrument [Line Items]                          
Borrowings outstanding       0           $ 0   0  
Revolving Credit Facility | Line of Credit                          
Debt Instrument [Line Items]                          
Maximum borrowing capacity     $ 600,000,000                   $ 355,000,000
Period for outstanding amounts prior to stated maturity     91 days                    
Liquidity requirement     $ 250,000,000                    
Reduced annual rate     0.75%             0.10%      
Letters of credit outstanding       78,152,000           $ 78,152,000   110,098,000  
Unused borrowing capacity       $ 521,848,000           $ 521,848,000   $ 489,902,000  
Revolving Credit Facility and TLA Facility | Line of Credit                          
Debt Instrument [Line Items]                          
Debt instrument, covenant, net leverage ratio, maximum       2.50           2.50      
Debt instrument, covenant, fixed charge coverage ratio, minimum       3.00           3.00      
Debt instrument, covenant, first lien gross leverage ratio, actual       0.19           0.19      
Debt instrument, covenant, net leverage ratio, actual       0.01           0.01      
Debt instrument, covenant, fixed charge coverage ratio, actual       31.93           31.93      
Revolving Credit Facility and TLA Facility | Line of Credit | Maximum                          
Debt Instrument [Line Items]                          
Debt instrument, covenant, first lien gross leverage ratio       1.50           1.50      
Series 2020 | WVEDA Solid Waste Disposal Facility Revenue Bonds at 5.45%                          
Debt Instrument [Line Items]                          
Letters of credit outstanding $ 53,090,000                        
Series 2021 | WVEDA Solid Waste Disposal Facility Revenue Bonds at 5.45%                          
Debt Instrument [Line Items]                          
Letters of credit outstanding $ 44,985,000