Basis of Presentation and Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017 home	Sep. 30, 2017 lot	Sep. 30, 2017	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Summary of Significant Accounting Policies [Line Items]
Threshold number of homes below a minimum threshold of profitability		10	10
Measurement threshold of likelihood of being realized (percent)				50.00%
Advertising costs					$ 17.5	$ 19.2	$ 18.0
Minimum
Summary of Significant Accounting Policies [Line Items]
Estimated time to develop, sell, construct and close all homes (in years)	3 years
Estimated future warranty costs as a percentage or revenue (percent)				0.30%
Minimum | Furniture, Fixtures, Computer and Office Equipment
Summary of Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Maximum
Summary of Significant Accounting Policies [Line Items]
Estimated time to develop, sell, construct and close all homes (in years)	5 years
Estimated future warranty costs as a percentage or revenue (percent)				1.20%
Maximum | Information systems
Summary of Significant Accounting Policies [Line Items]
Estimated useful life	5 years
Maximum | Furniture, Fixtures, Computer and Office Equipment
Summary of Significant Accounting Policies [Line Items]
Estimated useful life	7 years