Pension and Postretirement Benefits Net Periodic Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension and Other Postretirement Benefit Expense [Abstract]
Service cost	$ 527	$ 510	$ 1,029	$ 1,020
Interest expense	1,462	1,694	2,924	3,387
Expected return on plan assets	(1,555)	(1,677)	(3,109)	(3,354)
Amortization of prior service cost	41	49	83	97
Actuarial loss	850	557	1,699	1,114
Net periodic pension cost (benefit)	$ 1,325	$ 1,133	$ 2,626	$ 2,264