v3.26.1
Common Unit-Based Compensation Plan - LTIP Grants (Details) - ARLP LTIP - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Number of units          
Balance at the beginning of the period (in units)     1,192,243    
Granted (in units)     431,501    
Vested (in units)     (400,722)    
Forfeited (in units)     (91,086)    
Balance at the end of the period (in units) 1,131,936   1,131,936    
Weighted average grant date fair value per unit          
Balance at the beginning of the period (in dollars per unit)     $ 22.58    
Granted (in dollars per unit)     25.8    
Vested (in dollars per unit)     21.54    
Forfeited (in dollars per unit)     23.34    
Balance at the end of the period (in dollars per unit) $ 24.12   $ 24.12    
Intrinsic value (in dollars)          
Intrinsic value of outstanding grants (in dollars) $ 27,144   $ 27,144   $ 27,696
Other information          
Common units issued     230,777    
Unit-based compensation expense 2,300 $ 2,300 $ 4,000 $ 4,200  
Total unit-based obligation recorded 12,200   12,200    
Unrecognized compensation expense (in dollars) $ 15,100   $ 15,100    
Weighted-average period for recognition of expense     1 year 6 months