Restructuring and Other Costs - Schedule of Restructuring Charges Related to Active Restructuring Initiatives (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | $ 39.9 | $ (1.8) | $ 497.4 | $ 363.2 |
Restructuring and Related Cost, Cost Incurred to Date | 974.9 | | 974.9 | |
Restructuring and Related Cost, Expected Cost | 1,149.6 | | 1,149.6 | |
PP&E and Related Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 15.5 | (6.8) | 363.3 | 338.8 |
Restructuring and Related Cost, Cost Incurred to Date | 752.4 | | 752.4 | |
Restructuring and Related Cost, Expected Cost | 752.4 | | 752.4 | |
Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 4 | 0.8 | 41.9 | 18.6 |
Restructuring and Related Cost, Cost Incurred to Date | 92.3 | | 92.3 | |
Restructuring and Related Cost, Expected Cost | 94 | | 94 | |
Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 20.4 | 4.2 | 92.2 | 5.8 |
Restructuring and Related Cost, Cost Incurred to Date | 130.2 | | 130.2 | |
Restructuring and Related Cost, Expected Cost | 303.2 | | 303.2 | |
Corrugated Packaging [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 10.8 | 1.1 | 20.6 | 5.5 |
Restructuring and Related Cost, Cost Incurred to Date | 40.1 | | 40.1 | |
Restructuring and Related Cost, Expected Cost | 55.9 | | 55.9 | |
Corrugated Packaging [Member] | PP&E and Related Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 7.9 | 0.3 | 12.2 | 0.3 |
Restructuring and Related Cost, Cost Incurred to Date | 15.9 | | 15.9 | |
Restructuring and Related Cost, Expected Cost | 15.9 | | 15.9 | |
Corrugated Packaging [Member] | Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 1.5 | 0.2 | 6.8 | 4.2 |
Restructuring and Related Cost, Cost Incurred to Date | 16.5 | | 16.5 | |
Restructuring and Related Cost, Expected Cost | 16.5 | | 16.5 | |
Corrugated Packaging [Member] | Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 1.4 | 0.6 | 1.6 | 1 |
Restructuring and Related Cost, Cost Incurred to Date | 7.7 | | 7.7 | |
Restructuring and Related Cost, Expected Cost | 23.5 | | 23.5 | |
Consumer Packaging [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 9.7 | 1.4 | 17.8 | 4.6 |
Restructuring and Related Cost, Cost Incurred to Date | 55.1 | | 55.1 | |
Restructuring and Related Cost, Expected Cost | 58.4 | | 58.4 | |
Consumer Packaging [Member] | PP&E and Related Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 1 | | 1 | |
Restructuring and Related Cost, Cost Incurred to Date | 3.2 | | 3.2 | |
Restructuring and Related Cost, Expected Cost | 3.2 | | 3.2 | |
Consumer Packaging [Member] | Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 5.8 | 1.4 | 14.4 | 4.5 |
Restructuring and Related Cost, Cost Incurred to Date | 39.3 | | 39.3 | |
Restructuring and Related Cost, Expected Cost | 40.1 | | 40.1 | |
Consumer Packaging [Member] | Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 2.9 | | 2.4 | 0.1 |
Restructuring and Related Cost, Cost Incurred to Date | 12.6 | | 12.6 | |
Restructuring and Related Cost, Expected Cost | 15.1 | | 15.1 | |
Global Paper [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 9 | (7.1) | 440 | 348 |
Restructuring and Related Cost, Cost Incurred to Date | 840.2 | | 840.2 | |
Restructuring and Related Cost, Expected Cost | 986 | | 986 | |
Global Paper [Member] | PP&E and Related Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 6.6 | (7.5) | 349.5 | 336.9 |
Restructuring and Related Cost, Cost Incurred to Date | 721.9 | | 721.9 | |
Restructuring and Related Cost, Expected Cost | 721.9 | | 721.9 | |
Global Paper [Member] | Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | (3.4) | (0.8) | 15.7 | 9.9 |
Restructuring and Related Cost, Cost Incurred to Date | 27.3 | | 27.3 | |
Restructuring and Related Cost, Expected Cost | 28.2 | | 28.2 | |
Global Paper [Member] | Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 5.8 | 1.2 | 74.8 | 1.2 |
Restructuring and Related Cost, Cost Incurred to Date | 91 | | 91 | |
Restructuring and Related Cost, Expected Cost | 235.9 | | 235.9 | |
Distribution [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 5.2 | 1 | 6.3 | 1 |
Restructuring and Related Cost, Cost Incurred to Date | 7.5 | | 7.5 | |
Restructuring and Related Cost, Expected Cost | 8.8 | | 8.8 | |
Distribution [Member] | Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 0.9 | | 1.9 | |
Restructuring and Related Cost, Cost Incurred to Date | 2.1 | | 2.1 | |
Restructuring and Related Cost, Expected Cost | 2.1 | | 2.1 | |
Distribution [Member] | Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 4.3 | 1 | 4.4 | 1 |
Restructuring and Related Cost, Cost Incurred to Date | 5.4 | | 5.4 | |
Restructuring and Related Cost, Expected Cost | 6.7 | | 6.7 | |
Corporate, Non-Segment [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 5.2 | 1.8 | 12.7 | 4.1 |
Restructuring and Related Cost, Cost Incurred to Date | 32 | | 32 | |
Restructuring and Related Cost, Expected Cost | 40.5 | | 40.5 | |
Corporate, Non-Segment [Member] | PP&E and Related Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | | 0.4 | 0.6 | 1.6 |
Restructuring and Related Cost, Cost Incurred to Date | 11.4 | | 11.4 | |
Restructuring and Related Cost, Expected Cost | 11.4 | | 11.4 | |
Corporate, Non-Segment [Member] | Severance and Other Employee Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | (0.8) | | 3.1 | |
Restructuring and Related Cost, Cost Incurred to Date | 7.1 | | 7.1 | |
Restructuring and Related Cost, Expected Cost | 7.1 | | 7.1 | |
Corporate, Non-Segment [Member] | Other Restructuring Costs [Member] | | | | |
Restructuring Cost And Reserve [Line Items] | | | | |
Restructuring and Related Cost, Incurred Cost | 6 | $ 1.4 | 9 | $ 2.5 |
Restructuring and Related Cost, Cost Incurred to Date | 13.5 | | 13.5 | |
Restructuring and Related Cost, Expected Cost | $ 22 | | $ 22 | |