Inventory - Quantitative Unobservable Inputs (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2019 USD ($) home
Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price | $	$ 350
Closings per community per month | home	1
Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price | $	$ 615
Closings per community per month | home	4
Measurement Input, Discount Rate | Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.147
Measurement Input, Discount Rate | Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.168