Inventory - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026 USD ($) home community	Mar. 31, 2025 USD ($)	Mar. 31, 2026 USD ($) community home	Mar. 31, 2025 USD ($)	Sep. 30, 2025 USD ($) home
Inventory Disclosure [Abstract]
Number of homes under construction | home	2,322		2,322		1,800
Number of homes under construction, spec homes | home	1,306		1,306		1,078
Total, spec homes	$ 448,600		$ 448,600		$ 417,400
Number of homes under construction, in-process spec homes | home	893		893		577
In-process spec homes	$ 264,700		$ 264,700		$ 201,800
Number of homes under construction, finished spec homes | home	413		413		501
Finished spec homes	$ 183,900		$ 183,900		$ 215,600
Threshold number of homes below a minimum threshold of profitability | home			10
Number of projects in progress impaired (in community) | community	1		1
Total impairment charges on projects in progress	$ 1,295	$ 0	$ 1,295	$ 0
Total impairment charges on land held for sale	0	0	$ 1,045	0
Number of impaired land held for sale communities (in community) | community			2
Estimated fair value less cost to sell of land held for sale assets at time of impairment	14,000		$ 14,000
Abandonments charges	$ 0	$ 528	$ 1,325	$ 528