Employee Benefit Plans (Components of Postretirement Benefit Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning of year	$ 22,247	$ 20,791
Service cost for benefits earned during the period	1,073	1,026	$ 961
Interest cost on accumulated post retirement benefit	869	814	752
Net benefit payments and expense	644	443
Actuarial loss	(229)	59
Accumulated postretirement benefit obligation	23,316	22,247	$ 20,791
Liabilities:
Current liabilities	802	737
Non-currrent liabilities	22,514	21,510
Total post retirement benefit liability recognized in statement of financial position	23,316	22,247
Components included in accumulated other comprehensive income (loss):
Unrecognized net loss	(2,530)	(2,847)
Cumulative net periodic benefit cost (in excess of employer contribution)	$ 20,786	$ 17,944