Inventory - Quantitative Unobservable Inputs (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2019 USD ($) home	Mar. 31, 2019 USD ($) home
Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price | $	$ 350	$ 350
Closings per community per month | home	2	1
Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Average selling price | $	$ 615	$ 615
Closings per community per month | home	4	4
Measurement Input, Discount Rate | Minimum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.147	0.147
Measurement Input, Discount Rate, Three Months Ended | Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.164	0.164
Measurement Input, Discount Rate, Six Months Ended | Maximum
Quantitative unobservable inputs for inventory impairment [Line Items]
Discount rate	0.168	0.168