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PENSION AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 3,318
Additional contributions to the plans	$ 3,412		3,412
Settlement loss	518	$ 0	518	$ 0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			173
Additional contributions to the plans	$ 344		$ 344