Owned Inventory - Narrative (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($) home	Mar. 31, 2022 USD ($)	Mar. 31, 2023 USD ($) home	Mar. 31, 2022 USD ($)	Sep. 30, 2022 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,381		2,381		2,688
Number of homes under construction, spec homes | home	787		787		887
Total, spec homes	$ 222,000,000		$ 222,000,000		$ 246,500,000
Number of homes under construction, in-process spec homes | home	629		629		793
In-process spec homes	$ 156,600,000		$ 156,600,000		$ 208,700,000
Number of homes under construction, finished spec homes | home	158		158		94
Finished spec homes	$ 65,400,000		$ 65,400,000		$ 37,800,000
Threshold number of homes below a minimum threshold of profitability | home			10
Impairment of projects in process	0	$ 0	$ 0	$ 0
Total impairment charges on land held for sale	0	440,000	0	440,000
Fair value of impaired long-lived assets to be disposed of		900,000		900,000
Total abandonments charges	$ 111,000	$ 495,000	$ 301,000	$ 495,000