EMPLOYEE BENEFIT PLANS - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan [Abstract]
Service cost for benefits earned during the period	$ 157	$ 1,794	$ 311	$ 3,754
Interest cost on pension benefit obligation	3,838	4,377	7,589	9,158
Expected return on assets	(5,432)	(5,920)	(10,741)	(12,391)
Amortization of unrecognized losses	1,819	1,793	3,597	3,755
Net periodic pension cost	$ 382	$ 2,044	$ 756	$ 4,276