Commitments and Contingencies (Pace, Piedmont, Pasadena - Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2020	Jun. 30, 2021	Sep. 30, 2012	Sep. 30, 2008	Sep. 30, 2006
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 40,600,000			$ 42,000,000
Change in estimated exposure	$ 19,000,000	0
Pace, Florida | Discontinued operations
Loss Contingencies [Line Items]
Pretax environmental expense	$ 19,000,000				$ 42,000,000
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		10,700,000		$ 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		$ 11,300,000
Total anticipated exposure			$ 13,000,000