Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Dec. 01, 2022	Nov. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2023	Sep. 30, 2022	Sep. 30, 2021
Basis of Presentation and Significant Accounting Policies [Line Items]
Gain on sale of businesses					$ 11.1
Business interruption recovery related to ransomware incident			$ 5.0	$ 5.0
Gain on Business Interruption Insurance Recovery, Statement of Income or Comprehensive Income [Extensible Enumeration]			Cost of Goods and Services Sold	Cost of Goods and Services Sold
Ransomware other recoveries						$ 57.2	$ 15.0
Eaton, IN, and Aurora, IL [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Sale of uncoated recycled paperboard mills subject to working capital adjustment	$ 50.0
Sale proceeds received	25.0
Preliminary working capital settlement	0.9
Amount financed	25.0
Gain on sale of businesses	$ 11.1
Grupo Gondi [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Date of acquisition	Dec. 01, 2022
Percentage of remaining interest acquired	67.70%
Cash payment to acquire businesses	$ 969.8
RTS Packaging, LLC [Member] | Chattanooga, TN [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Planned sale of interior partitions converting operations and Chattanooga mill subject to working capital adjustment		$ 330.0
Transaction expected to close subject to satisfaction of closing conditions		2023
Accounting Standards Update 2021-10 [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted					true
Change in accounting principle, accounting standards update, adoption date					Oct. 01, 2022
Change in accounting principle, accounting standards update, immaterial effect					true
Accounting Standards Update 2021-08 [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted					true
Change in accounting principle, accounting standards update, adoption date					Oct. 01, 2022
Change in accounting principle, accounting standards update, immaterial effect					true
Accounting Standards Update 2020-04 [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted					true
Change in accounting principle, accounting standards update, adoption date					Oct. 01, 2022
Change in accounting principle, accounting standards update, immaterial effect					true