Owned Inventory - Narrative (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2024 USD ($) home	Mar. 31, 2023 USD ($)	Mar. 31, 2024 USD ($) home	Mar. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,829		2,829		2,163
Number of homes under construction, spec homes | home	1,084		1,084		779
Total, spec homes	$ 309,000,000		$ 309,000,000		$ 218,000,000
Number of homes under construction, in-process spec homes | home	903		903		645
In-process spec homes	$ 234,900,000		$ 234,900,000		$ 162,000,000
Number of homes under construction, finished spec homes | home	181		181		134
Finished spec homes	$ 74,100,000		$ 74,100,000		$ 56,000,000
Threshold number of homes below a minimum threshold of profitability | home			10
Impairment of projects in process	0	$ 0	$ 0	$ 0
Impairment charges on land held for sale	0	0	0	0
Abandonments charges	$ 0	$ 111,000	$ 0	$ 301,000