The number of markets the entity operates in as of the balance sheet date.

No definition available.

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- Definition

Number of Projects

+ References

No definition available.

+ Details

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- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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Balance Type:	credit
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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow from sale of buildings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

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- Details

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- Details

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- Details

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Data Type:	na
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- Details

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- Details

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Segment Information - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
Segment Information - Narrative (Details) $ in Millions	Mar. 31, 2019 USD ($) Projects Market State Segments OperatingDivisions	Mar. 31, 2018 USD ($)	Mar. 31, 2019 USD ($) Projects Market State	Mar. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Proceeds from Sale of Buildings			$ 83.8	$ 253.4
Gain (Loss) on Sale of Properties	$ 29.3	$ 1.1	31.3	14.5
Total assets	15,007.0		15,007.0		$ 14,114.6
Other Segments [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Sale of Properties	29.3	0.0	29.3	0.0
Total assets	$ 263.3		$ 263.3		198.9
Homebuilding [Member]
Segment Reporting Information [Line Items]
Number of housing construction markets \| Market	84		84
Number of housing construction states \| State	29		29
Number of home building operating divisions \| OperatingDivisions	51
Number of homebuilding reporting segments \| Segments	6
Gain (Loss) on Sale of Properties	$ 0.0	0.0	$ 2.0	13.4
Total assets	$ 12,885.8		$ 12,885.8		12,132.8
Forestar Group [Member]
Segment Reporting Information [Line Items]
Number of housing construction markets \| Market	41		41
Number of housing construction states \| State	17		17
Gain (Loss) on Sale of Properties	$ 0.0	$ 2.7	$ 0.9	$ 2.7
Total assets	984.9		984.9		893.1
Multifamily [Member] \| Other Segments [Member]
Segment Reporting Information [Line Items]
Proceeds from Sale of Buildings	73.4		73.4
Gain (Loss) on Sale of Properties	29.3		29.3
Total assets	$ 170.2		$ 170.2		$ 173.2
Asset under Construction [Member] \| Multifamily [Member] \| Other Segments [Member]
Segment Reporting Information [Line Items]
Number of Projects \| Projects	4		4
Assets Leased to Others [Member] \| Multifamily [Member] \| Other Segments [Member]
Segment Reporting Information [Line Items]
Number of Projects \| Projects	2		2