Commitments and Contingencies (Pace, Piedmont, Pasadena - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Sep. 30, 2012	Sep. 30, 2008	Sep. 30, 2006
Loss Contingencies [Line Items]
Pre-tax loss from discontinued operations	$ 19.0	$ 19.0
Pace, Florida
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	42.7	42.7			$ 42.0
Change in estimated exposure	19.0
Pace, Florida | Discontinued Operations
Loss Contingencies [Line Items]
Pretax environmental expense					42.0
Pace, Florida | Minimum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies					42.0
Pace, Florida | Maximum
Loss Contingencies [Line Items]
Estimate of possible exposure from environmental loss contingencies					$ 52.0
Piedmont, South Carolina
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	14.0	14.0		$ 24.0
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	$ 11.6	$ 11.6
Total anticipated exposure			$ 13.0