Inventory Inventory - Quantitative Unobservable Inputs (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2017 USD ($) home	Sep. 30, 2016 USD ($) home
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands) (a)	$ 405
Discount rate	12.83%
Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands) (a)		$ 355
Closings per community per month | home	1	2
Discount rate		14.15%
Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price (in thousands) (a)		$ 560
Closings per community per month | home	4	4
Discount rate		15.33%