Employee Benefit Plans (Components of net periodic post retirement benefit cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Postemployment Benefits [Abstract]
Service cost for benefits earned during the period	$ 1,108	$ 1,073	$ 1,026
Interest cost on accumulated postretirement benefit	943	869	814
Other components	70	58	88
Total other components of net periodic benefit costs	1,013	927	902
Net periodic postretirement benefit cost	$ 2,121	$ 2,000	$ 1,928