Employee Benefit Plans (Components of net periodic post retirement benefit cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Postemployment Benefits [Abstract]
Service cost for benefits earned during the period	$ 1,026	$ 961	$ 827
Interest cost on accumulated postretirement benefit	814	752	720
Other components	88	35	14
Net periodic postretirement benefit cost	$ 1,928	$ 1,748	$ 1,561