XML 123 R103.htm IDEA: XBRL DOCUMENT v3.8.0.1
COMPENSATION PLANS - LTIP Other Information (Details) - ARLP LTIP - USD ($)
$ in Millions
12 Months Ended
Feb. 08, 2018
Jan. 24, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Other information          
Share based compensation expense     $ 11.0 $ 12.7 $ 11.2
Total unit-based obligation recorded     21.8 $ 25.1  
Unrecognized compensation expense     $ 11.4    
Weighted-average period for recognition of expense     1 year 1 month 6 days    
Units for which vesting requirements were deemed satisfied     350,516 284,272 202,778
Common units issued upon vesting     222,011 176,319 128,150
Forfeited (in units)     35,516 11,765 3,934
Units granted     475,310 960,992 303,165
Units available for grant 2,100,000        
2015 Grants          
Other information          
Units for which vesting requirements were deemed satisfied   290,706      
Common units issued upon vesting 191,858        
Forfeited (in units)   12,459      
2018 Grants          
Other information          
Additional grants authorized (in units)   526,305      
Units granted   511,305