Segment Information - Additional Information (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Insurance proceeds received, net cash used for investing activities	$ 1.4
Corrugated Packaging [Member] | Hurricane Michael [Member]
Segment Reporting Information [Line Items]
Insurance proceeds received	32.3
Deferred insurance proceeds	2.8
Insurance proceeds from business interruption recoveries	11.7
Insurance proceeds for direct costs and property damage	20.6
Insurance proceeds received, net cash provided by operating activities	30.9
Insurance proceeds received, net cash used for investing activities	1.4
Corrugated Packaging [Member] | Hurricane Michael [Member] | Cost of Goods Sold [Member]
Segment Reporting Information [Line Items]
Reduction of cost of goods sold	$ 29.5
Insurance proceeds for direct costs and property damage		$ 20.0