Net Periodic Benefit Cost (Components of net periodic pension cost and net periodic postretirement benefit cost) (Details) - USD ($)	3 Months Ended				6 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Curtailments		$ 247,000
Pension Plans, Defined Benefiit
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 451,000		$ 513,000		$ 902,000	$ 1,030,000
Interest cost	4,116,000		3,033,000		8,231,000	5,492,000
Expected return on plan assets	(5,618,000)		(4,398,000)		(11,237,000)	(8,077,000)
Net amortization	796,000		911,000		1,590,000	1,820,000
Defined Benefit Plan, Curtailments	0		0		247,000	0
Net periodic pension (benefit) cost	(255,000)		59,000		$ (267,000)	$ 265,000
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	42,000	84,000	51,000	$ 102,000
Net periodic pension (benefit) cost	52,000	103,000	83,000	167,000
Amortization of plan net losses	$ 10,000	$ 19,000	$ 32,000	$ 65,000