Commitments and Contingencies (Pace, Piedmont, Pasadena Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2012	Sep. 30, 2008	Sep. 30, 2006
Loss Contingencies [Line Items]
Pretax environmental expense		$ 18,600,000	$ 18,300,000	$ 14,200,000
Pre-tax loss from discontinued operations	$ 19,000,000.0		$ 19,000,000.0
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		39,800,000					$ 42,000,000
Change in estimated exposure	$ 19,000,000	0
Pace, Florida | Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense							$ 42,000,000
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		9,500,000				$ 24,000,000
Piedmont, South Carolina | Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense						$ 24,000,000
Pasadena, Texas
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 11,200,000
Total anticipated exposure					$ 13,000,000