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, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Defined Benefit Plan Disclosure [Line Items]
Service costs			$ 1,226,000	$ 1,691,000
Interest cost			4,938,000	5,014,000
Expected return on plan assets			(5,606,000)	(5,376,000)
Net amortization			2,995,000	2,008,000
Defined Benefit Plan, Curtailments			1,172,000	1,172,000
Net periodic pension cost			3,553,000	4,509,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service costs	613,000	845,000
Interest cost	2,469,000	2,507,000
Expected return on plan assets	(2,803,000)	(2,688,000)
Net amortization	1,497,000	1,004,000
Defined Benefit Plan, Curtailments	0	0
Net periodic pension cost	1,776,000	1,668,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	78,000	120,000	156,000	239,000
Net amortization			72,000	164,000
Net periodic pension cost	114,000	202,000	228,000	403,000
Amortization of plan net losses	$ 36,000	$ 82,000