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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Additional) (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]      
Defined contribution plan, employer contribution, maximum percentage 6.00%    
Defined contribution plan, expense relating to the plan $ 4.2 $ 3.7  
Contributions made by the corporation to the plan $ 9.2    
Scenario, Forecast [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Estimated future contributions for the current fiscal year     $ 14.0