PENSION AND OTHER POSTRETIREMENT BENEFITS - Net Periodic Pension Costs (Details) - Pension Benefits - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 120	$ 116	$ 240	$ 232
Interest expense	1,155	1,063	2,309	2,126
Expected return on plan assets	(1,286)	(1,264)	(2,572)	(2,529)
Amortization of prior service cost	11	10	21	21
Settlement loss	518	0	518	0
Actuarial loss	422	511	845	1,022
Net periodic pension cost (benefit)	$ 940	$ 436	$ 1,361	$ 872