Inventory - Narrative (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2019 USD ($) home Community	Dec. 31, 2018 USD ($) Community	Sep. 30, 2019 USD ($) home
Inventory Disclosure [Abstract]
Number of substantially completed homes unsold | home	267		238
Total value of substantially completed homes | $	$ 90,200		$ 82,200
Threshold number of homes below a minimum threshold of profitability | home	10
Number of communities on watch list | Community	4	4
Inventory impairments and abandonments | $	$ 0	$ 1,007
Number of impaired communities | Community		1