Basis of Presentation and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Total revenue	$ 409,846	$ 565,339	$ 773,337	$ 1,034,292
Customer deposits	21,077		21,077		$ 14,260
Contract with customer, liability, revenue recognized	4,200		11,300
Homebuilding revenue
Disaggregation of Revenue [Line Items]
Total revenue	397,748	556,032	757,490	1,016,454
Land sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 12,098	$ 9,307	$ 15,847	$ 17,838