Owned Inventory - Narrative (Details)	3 Months Ended
	Dec. 31, 2024 USD ($) home	Dec. 31, 2023 USD ($)	Sep. 30, 2024 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,435		2,315
Number of homes under construction, spec homes | home	1,219		1,154
Total, spec homes	$ 395,700,000		$ 360,900,000
Number of homes under construction, in-process spec homes | home	894		827
In-process spec homes	$ 257,300,000		$ 231,400,000
Number of homes under construction, finished spec homes | home	325		327
Finished spec homes	$ 138,400,000		$ 129,500,000
Threshold number of homes below a minimum threshold of profitability | home	10
Impairment of projects in process	$ 0	$ 0
Impairment charges on land held for sale	0	0
Abandonments charges	$ 0	$ 0