Employee Benefit Plans (Components of net periodic benefit costs post retirement benefits) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Postemployment Benefits [Abstract]
Service cost for benefits earned during the period	$ 277	$ 268	$ 554	$ 536
Other components of net periodic benefit costs:
Interest cost on accumulated postretirement benefit	236	217	472	434
Other components	18	15	35	30
Total other components of net periodic benefit costs	254	232	507	464
Net periodic postretirement benefit cost	$ 531	$ 500	$ 1,061	$ 1,000