Inventory - Narrative (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2019 USD ($) home Community	Sep. 30, 2019 USD ($) home lot Community	Sep. 30, 2019 USD ($) home Community	Sep. 30, 2019 USD ($) home Community	Sep. 30, 2018 USD ($) home Community	Sep. 30, 2017 USD ($) Community
Real Estate [Abstract]
Land held for sale impairments			6
Number of substantially completed homes not subject to a sales contract | home	238	238	238	238	240
Total value of substantially completed homes | $	$ 82,200	$ 82,200	$ 82,200	$ 82,200	$ 84,800
Threshold number of homes below a minimum threshold of profitability	10	10
Number of communities on watch list	2	2	2	2	4
Number of communities on watch list, subject to additional quantitative analysis					2
Impairment charge | $				$ 110,030	$ 1,005	$ 1,693
Number of communities impaired			10		1	1