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, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Pension Plans, Defined Benefiit
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 269	$ 255	$ 784	$ 791
Interest cost	3,701	3,864	11,077	11,629
Expected return on plan assets	(3,971)	(4,594)	(11,917)	(13,836)
Net amortization	573	572	1,714	1,750
Net periodic pension (benefit) cost	572	97	1,658	334
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Interest cost	14	28	53	85
Net amortization	(74)	(112)	(154)	(136)
Net periodic pension (benefit) cost	$ (60)	$ (84)	$ (101)	$ (51)