Owned Inventory - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025 USD ($) community lot home	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) home lot community	Jun. 30, 2024 USD ($)	Sep. 30, 2024 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,539		2,539		2,315
Number of homes under construction, spec homes | home	1,376		1,376		1,154
Total, spec homes	$ 490,500		$ 490,500		$ 360,900
Number of homes under construction, in-process spec homes | home	1,004		1,004		827
In-process spec homes	$ 332,200		$ 332,200		$ 231,400
Number of homes under construction, finished spec homes | home	372		372		327
Finished spec homes	$ 158,300		$ 158,300		$ 129,500
Threshold number of homes below a minimum threshold of profitability | home			10
Number of communities impaired (in community) | community	2		2
Total impairment charges on projects in progress	$ 8,642	$ 0	$ 8,642	$ 0
Number of land held for sale lots impaired (in lot) | lot	38		38
Total impairment charges on land held for sale	$ 1,466	0	$ 1,466	0
Abandonments charges	231	200	759	200
Inventory impairments and abandonments	$ 10,339	$ 200	$ 10,867	$ 200