Inventory Inventory - Quantitative Unobservable Inputs (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2018 USD ($) home	Sep. 30, 2017 USD ($) home
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands) | $	$ 356	$ 405
Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Closings per community per month	1	1
Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Closings per community per month	6	4
Discount Rate
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.1511	0.1283