CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ 133	$ (2,193)	$ (17,060)	$ 840	$ (1,837)	$ 2,846	$ 20,728	$ 814	$ (18,280)	$ 22,551	$ 71,791
Other comprehensive income (loss), net of tax:
Unrealized (losses) gains on derivative instruments designated as cash flow hedges, net of tax									(5,922)
Losses (gains) on derivative instruments designated as cash flow hedges reclassified to cost of goods sold, net of tax									800
Change in the funded status of retiree benefit obligations, net of tax									4,576	7,466	(11,461)
Total comprehensive (loss) income, net of tax									$ (18,826)	$ 27,627	$ 70,974