Owned Inventory - Narrative (Details)	3 Months Ended		9 Months Ended
	Jun. 30, 2022 USD ($) home	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) home	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	3,656		3,656		2,912
Number of homes under construction, spec homes | home	936		936		576
Total, spec homes	$ 212,800,000		$ 212,800,000		$ 116,400,000
Number of homes under Construction, in-process spec homes | home	881		881		542
In-process spec homes	$ 191,000,000		$ 191,000,000		$ 105,200,000
Number of homes under construction, finished spec homes | home	55		55		34
Finished spec homes	$ 21,800,000		$ 21,800,000		$ 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	0	0	440,000	0
Total abandonments charges	$ 0	$ 231,000	$ 495,000	$ 696,000