Commitments and Contingencies (Pace, Piedmont, and Pasadena Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2012 USD ($) surfaceImpoundmentUnit	Sep. 30, 2008 USD ($)	Sep. 30, 2006 USD ($)
Loss Contingencies [Line Items]
Pretax environmental expense			$ 37.7	$ 27.0	$ 24.9
Pre-tax loss from discontinued operations	$ 10.6	$ 19.4	10.6	19.4
Environmental
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 79.1	$ 85.6	79.1
Accrual for environmental loss contingencies, maximum payout period			30 years
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 53.8						$ 42.0
Change in estimated exposure				19.0		$ 19.0
Pace, Florida | Environmental
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies, maximum payout period			30 years
Pace, Florida | Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense				$ 19.0		$ 19.0			$ 42.0
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 9.8					$ 24.0
Change in estimated exposure	9.0
Piedmont, South Carolina | Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense	$ 9.0							$ 24.0
Pasadena, Texas
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 9.9
Total anticipated exposure							$ 13.0
Number Of Closed Facilities | surfaceImpoundmentUnit							2