Net Periodic Benefit Cost (Components of net periodic pension cost and net periodic postretirement benefit cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Pension Plans, Defined Benefiit
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 517	$ 560
Interest cost	2,459	2,529
Expected return on plan assets	(3,679)	(3,549)
Net amortization	909	1,069
Net periodic pension cost	206	609
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	51	54
Net periodic pension cost	84	73
Amortization of plan net losses	$ 33	$ 19