Net Periodic Benefit Cost (Narratives) (Details) - USD ($) shares in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 16,324,000				$ 19,046,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (4,104,000)	$ (2,969,000)	$ 16,599,000	$ 18,579,000	$ (7,073,000)	$ 35,178,000
Effect of dilutive employee stock options and other share-based awards	0		295		0	300
Pension Plans, Defined Benefiit
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			$ 0			$ 0
Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year							$ 5,169,000