Changes in Accounting Principles and Corrections to Previously Issued Financial Statements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2016	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of LIFO Inventory				91.00%
Unrealized losses on derivative instruments designated as cash flow hedges, net of tax	$ (6,097)	$ (428)
Losses (gains) on derivative instruments designated as cash flow hedges reclassified to cost of goods sold, net of tax	1,460	(772)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ (7,623)	(359)
LIFO to FIFO Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax			$ 17,600
As Previously Reported | LIFO to FIFO Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized losses on derivative instruments designated as cash flow hedges, net of tax		(432)
Losses (gains) on derivative instruments designated as cash flow hedges reclassified to cost of goods sold, net of tax		4
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		$ (1,400)