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Related Party Disclosures (Details) $ in Millions	3 Months Ended		6 Months Ended
Related Party Disclosures (Details) $ in Millions	Mar. 31, 2026 USD ($) Lot	Mar. 31, 2025 USD ($) Lot	Mar. 31, 2026 USD ($) Lot	Mar. 31, 2025 USD ($) Lot	Sep. 30, 2025 USD ($) Lot
Related Party Transaction [Line Items]
Selling, general and administrative expense	$ 37.9	$ 38.4	$ 74.3	$ 74.3
Number of Units in Real Estate Property \| Lot	63,500		63,500		65,100
Residential lot sales	$ (331.4)	(346.9)	$ (566.6)	(594.2)
Tract sales and other	(42.9)	(4.1)	(80.7)	(7.1)
D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Selling, general and administrative expense			3.6	3.6
Employee Benefits and Share-Based Compensation			7.7	6.9
Costs and Expenses, Related Party			0.8	0.5
Related Party Transaction, Purchases from Related Party	0.1	0.1	0.4	0.1
Accrued Liabilities and Other Liabilities	5.2		5.2		$ 2.2
D.R. Horton, Inc. [Member] \| Deposits [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	1.8	4.6	3.5	14.6
D.R. Horton, Inc. [Member] \| Use Rights
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction				2.1
D.R. Horton, Inc. [Member] \| Other Preacquisition and Due Diligence Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 12.2	$ 4.0	$ 20.1	$ 8.2
D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Number of Lots Sold \| Lot	2,450	2,501	4,077	4,613
Residential lot sales	$ 284.4	$ 267.8	$ 468.2	$ 485.2
Deferred Revenue, Period Increase (Decrease)	0.0	0.0	$ 0.0	1.2
D.R. Horton, Inc. [Member] \| Minimum
Related Party Transaction [Line Items]
Related Party Transaction, Rate			12.00%
D.R. Horton, Inc. [Member] \| Maximum
Related Party Transaction [Line Items]
Related Party Transaction, Rate			16.00%
D.R. Horton, Inc. [Member] \| Land held for future development
Related Party Transaction [Line Items]
Tract sales and other	$ 14.8	$ 2.0	$ 20.2	$ 4.0
D.R. Horton, Inc. [Member] \| Under Contract [Member]
Related Party Transaction [Line Items]
Number of Units in Real Estate Property \| Lot	22,900		22,900		22,800
Related Party Deposit Liabilities	$ 200.0		$ 200.0		$ 179.7
Related Party Transaction, Purchase Obligation from Parent	$ 2,089.0		$ 2,089.0		$ 2,000.0
D.R. Horton, Inc. [Member] \| Right of First Offer [Member]
Related Party Transaction [Line Items]
Number of Units in Real Estate Property \| Lot	18,100		18,100		17,600