Income Taxes - Components of Net Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2017
Deferred Tax Assets
Net Operating Loss Carryforwards	$ 39,884	$ 81,920
Inventory Valuation and Reserves	10,023	20,428
Pension Benefits	15,750	24,824
Other Postretirement Benefits	3,996	5,959
Accrued Employee Benefits	15,697	18,409
Other Accrued Liabilities	9,386	8,609
Hedging Activities	1,477	5,409
Tax Credit and Other Carryforwards	644	37,603
Intangible Assets	0	14,947
Total	96,857	218,108
Valuation Allowance	(21,629)	(116,770)
Total Deferred Tax Assets	75,228	101,338
Deferred Tax Liabilities
Tax Depreciation in Excess of Book	77,106	83,258
Deferred Tax Liabilities, Intangible Assets	537	0
Deferred Tax Liabilities, Other	7,561	4,614
Total Deferred Tax Liabilities	85,204	87,872
Total Net Deferred Tax Liabilities	$ (9,976)	$ (13,466)