Property and Equipment (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($) Projects	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 823.2		$ 760.1
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(259.8)		(260.9)
Property, Plant and Equipment, Net	563.4		499.2
Depreciation	17.2	$ 15.9
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	350.5		329.4
2510 Household Furniture [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	130.3		128.3
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	124.5		128.6
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	90.7		71.6
Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	61.1		56.9
Multifamily [Member] | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	64.8		65.2
Multifamily [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	57.0		38.0
Multifamily [Member] | Other Property [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	74.9		50.7
Other Segments [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Net	267.6		221.2
Single Family [Member] | Assets Leased to Others [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 62.4		$ 37.0
Multifamily [Member] | Other Segments [Member] | Asset under Construction [Member]
Property, Plant and Equipment [Line Items]
Number of Projects | Projects	4
Multifamily [Member] | Other Segments [Member] | Assets Leased to Others [Member]
Property, Plant and Equipment [Line Items]
Number of Projects | Projects	1