Pension and Postretirement Benefits Net Periodic Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension and Other Postretirement Benefit Expense [Abstract]
Service cost	$ 120	$ 527	$ 240	$ 1,029
Interest expense	1,176	1,462	2,352	2,924
Expected return on plan assets	(1,403)	(1,555)	(2,806)	(3,109)
Amortization of prior service cost	10	41	20	83
Actuarial loss	524	850	1,048	1,699
Net periodic pension cost (benefit)	$ 427	$ 1,325	$ 854	$ 2,626