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COMMITMENTS AND CONTINGENCIES Employee Agreements (Details) - Unionized Employees Concentration Risk [Member]
12 Months Ended
Mar. 31, 2019
Concentration Risk [Line Items]  
Concentration Risk, Percentage 57.00%
Collective Bargaining Agreements, Maximum Annual Escalation Per Employee, Percent 4.50%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]  
Concentration Risk [Line Items]  
Concentration Risk, Percentage 78.00%