Owned Inventory - Narrative (Details)	3 Months Ended		9 Months Ended
	Jun. 30, 2024 USD ($) home	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) home	Jun. 30, 2023 USD ($)	Sep. 30, 2023 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,783		2,783		2,163
Number of homes under construction, spec homes | home	1,135		1,135		779
Total, spec homes	$ 353,300,000		$ 353,300,000		$ 218,000,000
Number of homes under construction, in-process spec homes | home	899		899		645
In-process spec homes	$ 261,100,000		$ 261,100,000		$ 162,000,000
Number of homes under construction, finished spec homes | home	236		236		134
Finished spec homes	$ 92,200,000		$ 92,200,000		$ 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	$ 200,000	$ 315,000	$ 200,000	$ 616,000