Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Deferred tax assets:
Inventory costs	$ 74.0	$ 63.5
Inventory impairments	9.5	12.7
Warranty and construction defect costs	239.5	190.5
Net operating loss carryforwards	44.1	11.7
Tax credit carryforwards	6.4	1.6
Incentive compensation plans	84.7	77.5
Other	12.7	15.6
Total deferred tax assets	470.9	373.1
Valuation allowance	(17.9)	(4.2)
Total deferred tax assets, net of valuation allowance	453.0	368.9
Deferred tax liabilities:
Deferral of profit on home closings	209.4	166.7
Depreciation of fixed assets	30.5	14.4
Deferred Tax Liabilities, Deferral of Income	18.5	2.0
Deferred Tax Liabilities, Undistributed Earnings of Subsidiary	27.3	10.2
Other	26.2	20.3
Total deferred tax liabilities	311.9	213.6
Deferred income taxes, net	141.1	155.3
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	44.1	$ 11.7
Vidler Water Resources, Inc.
Deferred tax assets:
Net operating loss carryforwards	30.9
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 30.9