XML 149 R66.htm IDEA: XBRL DOCUMENT v3.25.0.1
Current and Long-Term Financing (Narrative) (Details)
 12 Months Ended
Dec. 31, 2024
USD ($)
notePayable
unitOfEquipment
Dec. 31, 2023
USD ($)
Dec. 15, 2026
USD ($)
Line of Credit Facility [Line Items]      
Interest paid $ 5,300,000 $ 2,400,000  
Outstanding notes payable 99,430,000 35,800,000  
NACoal      
Line of Credit Facility [Line Items]      
Revolving credit agreement   10,000,000  
Line of credit facility, remaining borrowing capacity 99,102,000 105,120,000  
Secured Debt | NACoal      
Line of Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity 200,000,000.0    
Revolving credit agreement 70,000,000    
Line of credit facility, remaining borrowing capacity 99,100,000    
Amount of letters of credit outstanding $ 30,900,000    
Line of credit facility, unused capacity, commitment fee (percent) 0.40%    
Line of credit facility, average borrowing $ 27,200,000 $ 6,200,000  
Weighted average interest rate (percent) 8.83% 6.06%  
Fixed charge coverage ratio 1.10    
Secured Debt | NACoal | Demand Note Payable to Unconsolidated Subsidiary      
Line of Credit Facility [Line Items]      
Outstanding notes payable $ 7,700,000 $ 7,000,000.0  
Interest rate (percent) 4.15% 5.12%  
Secured Debt | NACoal | Notes Payable, Maturing at Various Dates Through 2030      
Line of Credit Facility [Line Items]      
Weighted average interest rate (percent) 5.50%    
Outstanding notes payable $ 21,800,000 $ 18,800,000  
Number of notes payable | notePayable 10    
Number of specified units of equipment | unitOfEquipment 13    
Secured Debt | NACoal | Notes Payable, Maturing December 2026 | Forecast      
Line of Credit Facility [Line Items]      
Principal payment due at maturity     $ 4,400,000
Secured Debt | NACoal | Maximum      
Line of Credit Facility [Line Items]      
Maximum debt to EBITDA ratio 2.75    
Maximum EBITDA ratio 1.50    
Secured Debt | NACoal | Minimum      
Line of Credit Facility [Line Items]      
Minimum interest coverage ratio 4.00    
Maximum EBITDA ratio 1.50    
Secured Debt | NACoal | Base Rate      
Line of Credit Facility [Line Items]      
Basis spread on variable rate (percent) 1.50%    
Secured Debt | NACoal | Secured Overnight Financing Rate      
Line of Credit Facility [Line Items]      
Basis spread on variable rate (percent) 2.50%