Net Periodic Benefit Cost (Components of net periodic pension cost and net periodic postretirement benefit cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Pension Plans, Defined Benefiit
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 615	$ 480	$ 1,645	$ 1,597
Interest cost	4,200	2,386	9,692	7,424
Expected return on plan assets	(5,848)	(3,582)	(13,925)	(10,678)
Net amortization	867	889	2,687	3,004
Defined Benefit Plan, Curtailments	0	82		82
Net periodic pension cost	(166)	255	99	1,429
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	40	53	142	161
Net periodic pension cost	42	72	209	218
Amortization of plan net losses	$ 2	$ 19	$ 67	$ 57