Employee Benefit Plans (Components of Postretirement Benefit Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning of year	$ 20,791	$ 18,554
Service cost for benefits earned during the period	1,026	961	$ 827
Interest cost on accumulated post retirement benefit	814	752	720
Net benefit payments and expense	(443)	(541)
Actuarial loss	59	1,065
Accumulated postretirement benefit obligation	22,247	20,791	$ 18,554
Liabilities:
Current liabilities	737	658
Non-currrent liabilities	21,510	20,133
Total post retirement benefit liability recognized in statement of financial position	22,247	20,791
Components included in accumulated other comprehensive income (loss):
Unrecognized net loss	(2,817)	(2,847)
Cumulative net periodic benefit cost (in excess of employer contribution)	$ 19,430	$ 17,944