Accounting Policies (Details) - USD ($) $ in Millions			12 Months Ended
	Sep. 30, 2021	Oct. 05, 2017	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 3.8		$ 3.8	$ 2.3
Accumulated depreciation	(0.9)		(0.9)	(1.2)
Property and equipment, net	$ 2.9		2.9	1.1
Depreciation			$ 0.4	0.3	$ 0.3
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period			4 years 6 months
Majority Shareholder [Member] | D.R. Horton, Inc. [Member]
Property, Plant and Equipment [Line Items]
Sale of Stock, Percentage of Ownership after Transaction	63.00%	75.00%
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 0.9		$ 0.9	1.2
Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2.9		$ 2.9	$ 1.1
Maximum | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life			10 years
Maximum | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life			10 years
Minimum | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life			5 years
Minimum | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life			2 years