Owned Inventory - Narrative (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2022 USD ($) home	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) home	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	3,568		3,568		2,912
Number of homes under construction, spec homes | home	775		775		576
Total, spec homes	$ 157,200,000		$ 157,200,000		$ 116,400,000
Number of homes under Construction, in-process spec homes | home	725		725		542
In-process spec homes	$ 139,000,000		$ 139,000,000		$ 105,200,000
Number of homes under construction, finished spec homes | home	50		50		34
Finished spec homes	$ 18,200,000		$ 18,200,000		$ 11,200,000
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	440,000	0	440,000	0
Total abandonments charges	$ 495,000	$ 0	$ 495,000	$ 465,000