Inventory - Narrative (Details)	3 Months Ended		9 Months Ended
	Jun. 30, 2021 USD ($) home	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) home	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) home
Inventory Disclosure [Abstract]
Number of substantially completed homes unsold | home	40		40		133
Total value of substantially completed homes	$ 12,000,000.0		$ 12,000,000.0		$ 42,200,000
Threshold number of homes below a minimum threshold of profitability | home			10
Impairment charges on land held for sale	0	$ 1,257,000	$ 0	$ 1,257,000
Abandonment charges	$ 231,000	$ 1,009,000	$ 696,000	$ 1,009,000