Commitments and Contingencies (Pace, Piedmont, Pasadena - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Sep. 30, 2012	Sep. 30, 2008	Sep. 30, 2006	Dec. 31, 2023	Sep. 30, 2023
Environmental
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies					$ 63.3	$ 64.5
Accrual for environmental loss contingencies, maximum payout period					27 years
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies				$ 42.0	$ 36.7
Change in estimated exposure	$ 19.0
Pace, Florida | Discontinued operations
Loss Contingencies [Line Items]
Pretax environmental expense	$ 19.0			$ 42.0
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 24.0		4.1
Piedmont, South Carolina | Discontinued operations
Loss Contingencies [Line Items]
Pretax environmental expense			$ 24.0
Pasadena, Texas
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies					$ 10.4
Total anticipated exposure		$ 13.0