PENSION AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2018	Jun. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 1,489
Additional contributions to the plans		$ 5,240
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 100
Additional contributions to the plans		$ 417

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration