ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Reclassifications Out of Accumulated Other Comprehensive Loss (Details) $ in Millions  | 
9 Months Ended | 
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 Sep. 30, 2019  
USD ($) 
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| Accumulated Other Comprehensive Income (Loss) [Line Items] | |
| Amounts reclassified from accumulated other comprehensive income (loss) | $ 9.0 | 
| Prior service cost | |
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |
| Total net periodic benefit cost, before tax | (0.6) | 
| Recognized actuarial loss | |
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |
| Total net periodic benefit cost, before tax | 12.0 | 
| Pension and other postretirement benefit plans | |
| Accumulated Other Comprehensive Income (Loss) [Line Items] | |
| Total net periodic benefit cost, before tax | 11.4 | 
| Total net periodic benefit cost, tax benefit | (2.4) | 
| Amounts reclassified from accumulated other comprehensive income (loss) | $ 9.0 | 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount before tax of reclassification adjustments of other comprehensive income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss). Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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