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ACCUMULATED OTHER COMPREHENSIVE INCOME AND OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Accumulated Other Comprehensive Loss        
Balance at the beginning of the period     $ (73.7)  
Other comprehensive income (loss) before reclassifications     (21.6)  
Amounts reclassified from accumulated other comprehensive loss, net of tax     (9.1)  
Other comprehensive loss attributable to Axiall, net of tax $ (11.3) $ (15.2) (30.7) $ (18.6)
Balance at the end of the period (104.4)   (104.4)  
Change in foreign currency translation adjustment        
Accumulated Other Comprehensive Loss        
Balance at the beginning of the period     (20.4)  
Other comprehensive income (loss) before reclassifications     (57.0)  
Other comprehensive loss attributable to Axiall, net of tax     (57.0)  
Balance at the end of the period (77.4)   (77.4)  
Change in derivative cash flow hedges        
Accumulated Other Comprehensive Loss        
Balance at the beginning of the period     (8.3)  
Other comprehensive income (loss) before reclassifications     13.0  
Amounts reclassified from accumulated other comprehensive loss, net of tax     (6.0)  
Other comprehensive loss attributable to Axiall, net of tax     7.0  
Balance at the end of the period (1.3)   (1.3)  
Change in pension and OPEB liability adjustments        
Accumulated Other Comprehensive Loss        
Balance at the beginning of the period     (45.0)  
Other comprehensive income (loss) before reclassifications     22.4  
Amounts reclassified from accumulated other comprehensive loss, net of tax     (3.1)  
Other comprehensive loss attributable to Axiall, net of tax     19.3  
Balance at the end of the period $ (25.7)   $ (25.7)