Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Property, Plant, and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property and Equipment [Line Items]
Property, Plant and Equipment, Net	$ 683.7	$ 499.2
Depreciation	69.4	66.1	$ 58.2
Intersegment Eliminations [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Net	(3.0)	0.0
Single Family [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	87.2	6.4
Other Segments [Member]
Property and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(28.2)	(20.9)
Property, Plant and Equipment, Net	308.9	221.2
Multifamily [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	232.1	154.1
Home Building [Member]
Property and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(256.2)	(231.6)
Property, Plant and Equipment, Net	372.8	272.4
Forestar Group [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Net	1.1	2.4
Financial Services [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Net	3.9	3.2
Building and Building Improvements [Member] \| Home Building [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	267.4	240.2
2510 Household Furniture [Member] \| Home Building [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	134.0	128.3
Furniture and Fixtures \| Other Segments [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	15.6	15.1
Furniture and Fixtures \| Home Building [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	108.1	107.4
Land [Member] \| Single Family [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	19.1	0.0
Land [Member] \| Other Segments [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	19.7	16.0
Land [Member] \| Multifamily [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	58.3	38.0
Land [Member] \| Home Building [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	32.3	21.7
Assets Leased to Others [Member] \| Single Family [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	68.1	6.4
Assets Leased to Others [Member] \| Multifamily [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	173.8	116.1
Other Assets \| Other Segments [Member]
Property and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 69.7	$ 56.9