Inventory Inventory - Quantitative Unobservable Inputs (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2019 USD ($) home	Sep. 30, 2018 USD ($) numberOfContract
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands)		$ 356
Discount rate		0.151
Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands)	$ 350
Closings per community per month	1	1
Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands)	$ 615
Closings per community per month	4	6
Discount Rate | Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.147
Discount Rate | Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.168