Forestar (FOR) 10-Q 28 Jan 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2019	Jan. 22, 2020
Entity Information [Line Items]
Entity Current Reporting Status	Yes
Document Type	10-Q
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2020
Trading Symbol	FOR
Title of 12(b) Security	Common Stock, par value $1.00 per share
Entity Registrant Name	FORESTAR GROUP INC.
Entity Central Index Key	0001406587
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		48,025,359
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
ASSETS
Cash and cash equivalents	$ 373.3	$ 382.8
Real estate	1,066.8	1,028.9
Investment in unconsolidated ventures	5.9	7.3
Income taxes receivable	3.8	3.2
Property and equipment, net	0.9	2.4
Deferred tax asset, net	11.8	17.4
Other assets	17.4	13.7
Total assets	1,479.9	1,455.7
LIABILITIES
Accounts payable	19.8	16.8
Earnest money deposits on sales contracts	89.7	89.9
Accrued expenses and other liabilities	82.7	79.6
Debt	462.1	460.5
Total liabilities	654.3	646.8
Commitments and contingencies (Note 13)
Forestar Group Inc. shareholders’ equity:
Common stock, par value $1.00 per share, 200,000,000 authorized shares, 48,025,359 and 47,997,366 shares issued and outstanding at December 31, 2019 and September 30, 2019, respectively	48	48
Additional paid-in capital	602.5	602.2
Retained earnings	175	158.1
Stockholders' equity	825.5	808.3
Noncontrolling interests	0.1	0.6
Total equity	825.6	808.9
Total liabilities and equity	$ 1,479.9	$ 1,455.7

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Dec. 31, 2019	Sep. 30, 2019
Equity [Abstract]
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	48,025,359	47,997,366
Common Stock, Par or Stated Value Per Share	$ 1	$ 1

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenues	$ 247.2	$ 38.5
Cost of sales	216.6	30.7
Selling, general and administrative expense	10.5	5.7
Equity in earnings of unconsolidated ventures	(0.5)	(0.6)
Loss (gain) on sale of assets	0.1	(0.9)
Interest and other income	(1.7)	(1.3)
Income before income taxes	22.2	4.9
Income tax expense	5.4	1
Net income	16.8	3.9
Net income (loss) attributable to noncontrolling interests	(0.1)	0.6
Net income attributable to Forestar Group Inc.	$ 16.9	$ 3.3
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)	48,011,132	41,952,493
Diluted (in shares)	48,066,418	41,958,699
Earnings Per Share [Abstract]
Earnings Per Share, Basic	$ 0.35	$ 0.08
NET INCOME (LOSS) PER DILUTED SHARE
Earnings Per Share, Diluted	$ 0.35	$ 0.08

Consolidated Statements of Tota

Consolidated Statements of Total Equity (Unaudited) Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
Beginning balances (shares) at Sep. 30, 2018		41,939,403
Stock issued under employee incentive plans (shares)		20,463
Ending balances (shares) at Dec. 31, 2018		41,959,866
Beginning balances at Sep. 30, 2018	$ 674.5	$ 41.9	$ 506.3	$ 125.1	$ 1.2
Net income	3.9	0	0	3.3	0.6
Stock issued under employee incentive plans	(0.1)	0.1	0	0	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(0.1)	0	0.1	0	0
Stock-based compensation expense	0.1	0	0.1	0	0
Distributions to noncontrolling interests	(0.5)	0	0	0	(0.5)
Ending balances at Dec. 31, 2018	678	$ 42	506.3	128.4	1.3
Beginning balances (shares) at Sep. 30, 2019		47,997,366
Stock issued under employee incentive plans (shares)		27,993
Ending balances (shares) at Dec. 31, 2019		48,025,359
Beginning balances at Sep. 30, 2019	808.9	$ 48	602.2	158.1	0.6
Net income	16.8	0	0	16.9	(0.1)
Stock issued under employee incentive plans	0	0	0	0	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(0.2)	0	0.2	0	0
Stock-based compensation expense	0.5	0	0.5	0	0
Distributions to noncontrolling interests	(0.4)	0	0	0	(0.4)
Ending balances at Dec. 31, 2019	$ 825.6	$ 48	$ 602.5	$ 175	$ 0.1

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net income	$ 16.8	$ 3.9
Adjustments:
Depreciation and amortization	1.9	1.4
Deferred income taxes	5.6	1.4
Equity in earnings of unconsolidated ventures	(0.5)	(0.6)
Distributions of earnings of unconsolidated ventures	0	4.9
Stock-based compensation expense	0.5	0.1
Asset impairments	0.3	0.4
Loss (gain) on sale of assets	0.1	(0.9)
Changes in operating assets and liabilities:
Increase in real estate	38.2	195.2
Increase in other assets	(0.7)	(1.3)
Increase in accounts payable and other accrued liabilities	3.4	3.1
(Decrease) increase in earnest money deposits on sales contracts	(0.2)	18.8
Increase in income taxes receivable	(0.6)	(0.1)
Net cash used in operating activities	(11.6)	(164.1)
INVESTING ACTIVITIES
Expenditures for property, equipment, software and other	0	(0.1)
Return of investment in unconsolidated ventures	1.8	0.1
Proceeds from sale of assets	1.3	0
Net cash provided by investing activities	3.1	0
FINANCING ACTIVITIES
Deferred financing fees	(0.4)	0
Distributions to noncontrolling interests, net	(0.4)	(0.5)
Settlement of equity awards	(0.2)	(0.1)
Net cash used in financing activities	(1)	(0.6)
Net decrease in cash and cash equivalents	(9.5)	(164.7)
Cash and cash equivalents	$ 373.3	$ 170.3

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited, consolidated financial statements include the accounts of Forestar Group Inc. (Forestar) and all of its 100% owned, majority-owned and controlled subsidiaries, which are collectively referred to as the Company unless the context otherwise requires. The Company accounts for its investment in other entities in which it has significant influence over operations and financial policies using the equity method. All intercompany accounts, transactions and balances have been eliminated in consolidation. Noncontrolling interests in consolidated pass-through entities are recognized before income taxes. The transactions included in net income in the consolidated statements of operations are the same as those that would be presented in comprehensive income. Thus, the Company's net income equates to comprehensive income. The financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, these financial statements reflect all adjustments considered necessary to fairly state the results for the interim periods shown, including normal recurring accruals and other items. These financial statements, including the consolidated balance sheet as of September 30, 2019 , which was derived from audited financial statements, do not include all of the information and notes required by GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s annual report on Form 10-K for the fiscal year ended September 30, 2019 . In October 2017 , Forestar became a majority-owned subsidiary of D.R. Horton, Inc. (D.R. Horton) by virtue of a merger with a wholly-owned subsidiary of D.R. Horton. Immediately following the merger, D.R. Horton owned 75% of the Company's outstanding common stock. In connection with the merger, the Company entered into certain agreements with D.R. Horton including a Stockholder’s Agreement, a Master Supply Agreement, and a Shared Services Agreement. D.R. Horton is considered a related party of Forestar under GAAP. At December 31, 2019 , D.R. Horton owned approximately 65% of the Company's outstanding common stock. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions. These estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates. Adoption of New Accounting Standard In February 2016, the FASB issued ASU 2016-02, “Leases,” which requires that lease assets and liabilities be recognized on the balance sheet and that key information about leasing arrangements be disclosed. The guidance was effective for the Company beginning October 1, 2019 and did not have a material impact on its consolidated financial position, results of operations or cash flows. As a result of the adoption of this standard on October 1, 2019, the Company recorded right of use assets of $ 2.7 million and lease liabilities of $2.9 million . Lease right of use assets are included in other assets and lease liabilities are included in accrued expenses and other liabilities in the consolidated balance sheet. Pending Accounting Standards In December 2019, the FASB issued ASU 2019-12 related to simplifying the accounting for income taxes. The guidance is effective for the Company beginning October 1, 2021, although early adoption is permitted. The Company is currently evaluating the impact of this guidance, and it is not expected to have a material impact on its consolidated financial position, results of operations and cash flows.

Segment Information

Segment Information	3 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information The Company manages its operations through its real estate segment. The Company's real estate segment is its core business and generates substantially all of the Company’s revenues. The real estate segment primarily acquires land and develops infrastructure for single-family residential communities. The Company's real estate segment generates its revenues principally from sales of residential single-family finished lots to local, regional and national homebuilders. The Company has other business activities for which the related assets and results of operations are immaterial and therefore are included within the Company's real estate segment.

Real Estate

Real Estate	3 Months Ended
	Dec. 31, 2019
Real Estate [Abstract]
Real Estate	Real Estate Real estate consists of: December 31, September 30, (In millions) Developed and under development projects $ 1,051.4 $ 1,011.8 Undeveloped land 15.4 17.1 $ 1,066.8 $ 1,028.9 In the three months ended December 31, 2019 , the Company invested $122.2 million for the acquisition of residential real estate and $114.0 million for the development of residential real estate. At December 31, 2019 and September 30, 2019 , undeveloped land primarily consists of undeveloped land which the Company has the contractual right to sell to D.R. Horton within approximately one year of its purchase or, if D.R. Horton elects, at an earlier date, at a sales price equal to the carrying value of the land at the time of sale plus additional consideration which ranges from 12% to 16% per annum.

Revenues Revenues (Notes)

Revenues Revenues (Notes)	3 Months Ended
	Dec. 31, 2019
Revenues [Abstract]
Revenue from Contract with Customer [Text Block]	Revenues Revenues consist of: Three Months Ended December 31, 2019 2018 (In millions) Residential lot sales $ 217.1 $ 34.7 Residential tract sales 30.0 — Commercial tract sales — 3.5 Other 0.1 0.3 $ 247.2 $ 38.5

Capitalized Interest (Notes)

Capitalized Interest (Notes)	3 Months Ended
	Dec. 31, 2019
Capitalized Interest [Abstract]
Capitalized Interest [Text Block]	Capitalized Interest The Company capitalizes interest costs to real estate throughout the development period (active real estate). Capitalized interest is charged to cost of sales as the related real estate is sold to the buyer. During periods in which the Company’s active real estate is lower than its debt level, a portion of the interest incurred is reflected as interest expense in the period incurred. During the first quarter of fiscal 2020 and fiscal year 2019, the Company’s active real estate exceeded its debt level, and all interest incurred was capitalized to real estate. The following table summarizes the Company’s interest costs incurred, capitalized and expensed during the three months ended December 31, 2019 and 2018 . Three Months Ended December 31, 2019 2018 (In millions) Capitalized interest, beginning of period $ 23.7 $ 3.2 Interest incurred 9.9 2.8 Interest charged to cost of sales (3.8 ) (0.7 ) Capitalized interest, end of period $ 29.8 $ 5.3

Investment in Unconsolidated Ve

Investment in Unconsolidated Ventures	3 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Ventures	Investment in Unconsolidated Ventures At December 31, 2019 , the Company had ownership interests in four ventures that it accounted for using the equity method. Combined summarized balance sheet and income statement information for these unconsolidated ventures follows: December 31, September 30, (In millions) Assets: Cash and cash equivalents $ 1.4 $ 1.6 Real estate 10.1 13.6 Other assets 0.2 0.1 Total assets $ 11.7 $ 15.3 Liabilities and Equity: Accounts payable and other liabilities $ 0.3 $ 0.3 Equity 11.4 15.0 Total liabilities and equity $ 11.7 $ 15.3 Forestar's investment in unconsolidated ventures $ 5.9 $ 7.3 Three Months Ended December 31, 2019 2018 (In millions) Revenues $ 2.0 $ 1.8 Earnings $ 1.4 $ 1.4 Forestar's equity in earnings of unconsolidated ventures $ 0.5 $ 0.6

Other Assets, Accrued Expenses

Other Assets, Accrued Expenses and Other Liabilities	3 Months Ended
	Dec. 31, 2019
Other Assets, Accrued Expenses and Other Liabilities [Abstract]
Other Assets And Other Liabilities [Text Block]	Other Assets, Accrued Expenses and Other Liabilities The Company's other assets at December 31, 2019 and September 30, 2019 were as follows: December 31, September 30, (In millions) Receivables, net $ 1.1 $ 1.1 Lease right of use assets 2.7 — Prepaid expenses 2.4 3.4 Land purchase contract deposits 5.0 5.1 Other assets 6.2 4.1 $ 17.4 $ 13.7 The Company's accrued expenses and other liabilities at December 31, 2019 and September 30, 2019 were as follows: December 31, September 30, (In millions) Accrued employee compensation and benefits $ 4.9 $ 5.6 Accrued property taxes 1.8 2.1 Accrued interest 7.4 13.5 Contract liabilities 4.0 2.5 Deferred income 9.3 9.3 Accrued development costs 38.9 35.4 Other accrued expenses 10.6 8.4 Other liabilities 5.8 2.8 $ 82.7 $ 79.6

Debt, net

Debt, net	3 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt, net	Debt The Company's notes payable at their principal amounts, net of unamortized discounts and debt issuance costs, consist of the following: December 31, September 30, (In millions) Unsecured: 3.75% convertible senior notes due 2020 $ 118.0 $ 116.7 8.0% senior notes due 2024 344.1 343.8 Revolving credit facility — — $ 462.1 $ 460.5 Bank Credit Facility The Company has a $380 million senior unsecured revolving credit facility with an uncommitted accordion feature that could increase the size of the facility to $570 million , subject to certain conditions and availability of additional bank commitments. The facility also provides for the issuance of letters of credit with a sublimit equal to the greater of $100 million and 50% of the revolving credit commitment. Borrowings under the revolving credit facility are subject to a borrowing base based on the book value of the Company's real estate assets and unrestricted cash. Letters of credit issued under the facility reduce the available borrowing capacity. At December 31, 2019 , there were no borrowings outstanding and $28.7 million of letters of credit issued under the revolving credit facility, resulting in available capacity of $351.3 million . There were no borrowings or repayments under the facility during the three months ended December 31, 2019 . In October 2019 , the revolving credit facility was amended to extend its maturity date to October 2, 2022 . The maturity date may be extended by up to one year on up to two additional occasions, subject to the approval of lenders holding a majority of the commitments. The revolving credit facility includes customary affirmative and negative covenants, events of default and financial covenants. The financial covenants require a minimum level of tangible net worth, a minimum level of liquidity, and a maximum allowable leverage ratio. These covenants are measured as defined in the credit agreement governing the facility and are reported to the lenders quarterly. A failure to comply with these financial covenants could allow the lending banks to terminate the availability of funds under the revolving credit facility or cause any outstanding borrowings to become due and payable prior to maturity. At December 31, 2019 , the Company was in compliance with all of the covenants, limitations and restrictions of its revolving credit facility. 3.75% Convertible Senior Notes due 2020 At December 31, 2019 , the principal amount of the 3.75% convertible senior notes due March 2020 was $118.9 million and the unamortized debt discount was $0.8 million . The effective interest rate on the liability component was 8.0% and the carrying amount of the equity component was $16.8 million . The Company intends to settle the principal amount of these notes in cash, with any excess conversion value to be settled in shares of its common stock. At December 31, 2019 and September 30, 2019 , the Company had $0.1 million and $0.2 million in unamortized deferred financing fees that were deducted from the carrying value of these notes. 8.0% Senior Notes due 2024 In April 2019 , the Company issued $350 million principal amount of 8.0% senior notes pursuant to Rule 144A and Regulation S under the Securities Act of 1933, as amended (the "Securities Act"). The notes mature April 15, 2024 with interest payable semi-annually and represent senior unsecured obligations that rank equally in right of payment to all existing and future senior unsecured indebtedness. The notes may be redeemed prior to maturity, subject to certain limitations and premiums defined in the indenture agreement. On or after April 15, 2021, the notes may be redeemed at 104% of their principal amount plus any accrued and unpaid interest. The redemption price decreases annually on a ratable basis to par by April 15, 2023 in accordance with the indenture. The notes are guaranteed by each of the Company's subsidiaries to the extent such subsidiaries guarantee the Company's revolving credit facility. At December 31, 2019 and September 30, 2019 , the Company had $5.9 million and $6.2 million in unamortized deferred financing fees that were deducted from the carrying value of these notes. The annual effective interest rate of the notes after giving effect to the amortization of financing costs is 8.5% . The indenture governing the notes requires that, upon the occurrence of both a Change of Control and a Rating Decline (each as defined in the indenture), the Company offer to purchase the notes at 101% of their principal amount. If the Company or its restricted subsidiaries dispose of assets, under certain circumstances, the Company will be required to either invest the net cash proceeds from such asset sales in its business within a specified period of time, repay certain senior secured debt or debt of its non-guarantor subsidiaries, or make an offer to purchase a principal amount of the notes equal to the excess net cash proceeds at a purchase price of 100% of their principal amount. The indenture contains covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries to pay dividends or distributions, repurchase equity, prepay subordinated debt and make certain investments; incur additional debt or issue mandatorily redeemable equity; incur liens on assets; merge or consolidate with another company or sell or otherwise dispose of all or substantially all of the Company’s assets; enter into transactions with affiliates; and allow to exist certain restrictions on the ability of subsidiaries to pay dividends or make other payments. At December 31, 2019 , the Company was in compliance with all of the limitations and restrictions associated with its senior note obligations.

Fair Value

Fair Value	3 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value	Fair Value Measurements Fair value is the exchange price that would be received for an asset or paid to transfer a liability in an orderly transaction between market participants. In arriving at a fair value measurement, the Company uses a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable. The three levels of inputs used to establish fair value are the following: • Level 1 — Quoted prices in active markets for identical assets or liabilities; • Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and • Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company elected not to use the fair value option for cash and cash equivalents, restricted cash and debt. For the financial assets and liabilities that the Company does not reflect at fair value, the following tables present both their respective carrying value and fair value at December 31, 2019 and September 30, 2019 . Fair Value at December 31, 2019 Carrying Value Level 1 Level 2 Level 3 Total (in millions) Cash and cash equivalents (a) $ 373.3 $ 373.3 $ — $ — $ 373.3 Debt (b) 462.1 — 501.1 — 501.1 Fair Value at September 30, 2019 Carrying Value Level 1 Level 2 Level 3 Total (in millions) Cash and cash equivalents (a) $ 382.8 $ 382.8 $ — $ — $ 382.8 Debt (b) 460.5 — 497.3 — 497.3 _____________________ (a) The fair values of cash and cash equivalents approximate their carrying values due to their short-term nature and are classified as Level 1 within the fair value hierarchy. (b) At December 31, 2019 and September 30, 2019 , debt consisted of the Company's senior and convertible senior notes. The fair value of the senior notes is determined based on quoted prices, which is classified as Level 2 within the fair value hierarchy. Non-financial assets measured at fair value on a non-recurring basis principally include real estate assets which the Company reviews for indicators of potential impairment and performs impairment evaluations when necessary. Real estate impairment charges are included in cost of sales in the Company's consolidated statements of operations.

Net Income (Loss) per Share

Net Income (Loss) per Share	3 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Income (Loss) per Share	Earnings per Share The computations of basic and diluted earnings per share are as follows: Three Months Ended December 31, 2019 2018 (In millions, except share data) Numerator: Net income attributable to Forestar Group Inc. $ 16.9 $ 3.3 Denominator: Weighted average common shares outstanding — basic 48,011,132 41,952,493 Dilutive effect of share based compensation 55,286 6,206 Total weighted average shares outstanding — diluted 48,066,418 41,958,699 Anti-dilutive awards excluded from diluted weighted average shares — — Basic net income per common share attributable to Forestar Group Inc. $ 0.35 $ 0.08 Diluted net income per common share attributable to Forestar Group Inc. $ 0.35 $ 0.08 The Company intends to settle the principal amount of its convertible senior notes in cash with any excess conversion value to be settled in shares of its common stock. Therefore, only the amount in excess of the par value of the notes will be included in the calculation of diluted net income per share using the treasury stock method. As such, the notes have no impact on diluted net income per share until the price of the Company's common stock exceeds the conversion price of the notes of $51.42 . The price of the Company's common stock did not exceed the conversion price in any of the periods presented.

Income Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s income tax expense for the three months ended December 31, 2019 and 2018 was $5.4 million and $1.0 million , respectively. The Company's effective tax rate was 24% for the three months ended December 31, 2019 compared to 21% in the prior year period. The Company's effective tax rate for both periods includes an expense for state income taxes and nondeductible expenses, and the tax rate in the prior year period included a tax benefit related to noncontrolling interests. At December 31, 2019 and September 30, 2019 , deferred tax assets, net of deferred tax liabilities, were $15.1 million and $20.7 million , offset by a valuation allowance of $3.3 million at both dates for the portion of the deferred tax assets that the Company has determined is more likely than not to be unrealizable. The valuation allowance was recorded because it is more likely than not that a portion of the Company's state deferred tax assets, primarily net operating loss (NOL) carryforwards, will not be realized because the Company is no longer operating in some states or the NOL carryforward periods are too brief to realize the related deferred tax asset. The Company will continue to evaluate both the positive and negative evidence in determining the need for a valuation allowance on its deferred tax assets. Any reversal of the valuation allowance in future periods will impact the effective tax rate. The Company's unrecognized tax benefits totaled $1.3 million at December 31, 2019 , all of which would affect its effective tax rate, if recognized.

Stockholders' Equity (Notes)

Stockholders' Equity (Notes)	3 Months Ended
	Dec. 31, 2019
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	Stockholders' Equity The Company has an effective shelf registration statement filed with the Securities and Exchange Commission (SEC) in September 2018 registering $500 million of equity securities. In September 2019 , the Company issued 6.0 million shares of its common stock for $17.50 per share in a public underwritten offering. Following the offering, $394.3 million remains available for issuance under the shelf registration statement.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Contractual Obligations and Off-Balance Sheet Arrangements In support of the Company's residential lot development business, it issues letters of credit under the revolving credit facility and has a surety bond program that provides financial assurance to beneficiaries related to the execution and performance of certain development obligations. At December 31, 2019 , the Company had outstanding letters of credit of $28.7 million under the revolving credit facility and surety bonds of $170.4 million , issued by third parties to secure performance under various contracts. The Company expects that its performance obligations secured by these letters of credit and bonds will generally be completed in the ordinary course of business and in accordance with the applicable contractual terms. When the Company completes its performance obligations, the related letters of credit and bonds are generally released shortly thereafter, leaving the Company with no continuing obligations. The Company has no material third-party guarantees. Litigation The Company is involved in various legal proceedings that arise from time to time in the ordinary course of business and believes that adequate reserves have been established for any probable losses. The Company does not believe that the outcome of any of these proceedings will have a significant adverse effect on its financial position, long-term results of operations or cash flows. It is possible, however, that charges related to these matters could be significant to the Company's results or cash flows in any one accounting period.

Related Party Transactions (Not

Related Party Transactions (Notes)	3 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	Related Party Transactions In October 2017 , the Company entered into a Shared Services Agreement with D.R. Horton whereby D.R. Horton provides the Company with certain administrative, compliance, operational and procurement services. During the three months ended December 31, 2019 and 2018 , the Company paid D.R. Horton $1.3 million and $0.5 million for these shared services and $0.6 million and $0.3 million for the cost of health insurance and other employee benefits. These expenses are included in selling, general and administrative expense in the consolidated statements of operations. Under the terms of the Master Supply Agreement with D.R. Horton, both companies identify land development opportunities to expand Forestar's portfolio of assets. At December 31, 2019 and September 30, 2019 , the Company owned or controlled through option purchase contracts approximately 44,500 and 38,300 residential lots, of which D.R. Horton had the following involvement. December 31, September 30, (Dollars in millions) Residential lots under contract to sell to D.R. Horton 12,700 12,800 Residential lots subject to right of first offer with D.R. Horton 12,900 10,600 Earnest money deposits from D.R. Horton for lots under contract $ 87.5 $ 88.7 Remaining purchase price of lots under contract with D.R. Horton $ 918.6 $ 953.8 In the three months ended December 31, 2019 and 2018 , the Company's residential lot sales totaled 2,422 and 518 , and lot sales revenues were $217.1 million and $34.7 million . Lot and land sales to D.R. Horton during those periods were as follows. Three Months Ended December 31, 2019 2018 (Dollars in millions) Residential single-family lots sold to D.R. Horton 2,390 455 Residential lot sales revenues from sales to D.R. Horton $ 215.6 $ 32.6 Residential tract acres sold to D.R. Horton 36 — Residential tract sales revenues from sales to D.R. Horton $ 7.2 $ — In addition, the increase in contract liabilities decreased revenues on lot sales to D.R. Horton by $1.5 million in the three months ended December 31, 2019 and decreased revenues by $3.6 million in the three months ended December 31, 2018 . During the three months ended December 31, 2019 and 2018 , the Company reimbursed D.R. Horton approximately $10.7 million and $12.1 million for previously paid earnest money and $5.2 million and $3.0 million for pre-acquisition and other due diligence and development costs related to land purchase contracts whereby D.R. Horton assigned its rights under these land purchase contracts to the Company. During the three months ended December 31, 2019 and 2018 , the Company paid D.R. Horton $1.5 million and $0.5 million for land development services. These amounts are included in cost of sales in the Company’s consolidated statements of operations. At December 31, 2019 and September 30, 2019 , undeveloped land was $15.4 million and $ 17.1 million . Undeveloped land primarily consists of undeveloped land which the Company has the contractual right to sell to D.R. Horton within approximately one year of its purchase or, if D.R. Horton elects, at an earlier date, at a sales price equal to the carrying value of the land at the time of sale plus additional consideration which ranges from 12% to 16% per annum. At December 31, 2019 and September 30, 2019 , accrued expenses and other liabilities on the Company's consolidated balance sheets included $2.8 million and $2.2 million owed to D.R. Horton for any accrued and unpaid shared service charges, land purchase contract deposits and due diligence and other development cost reimbursements.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions. These estimates and assumptions affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates.
Basis of Presentation	Basis of Presentation The accompanying unaudited, consolidated financial statements include the accounts of Forestar Group Inc. (Forestar) and all of its 100% owned, majority-owned and controlled subsidiaries, which are collectively referred to as the Company unless the context otherwise requires. The Company accounts for its investment in other entities in which it has significant influence over operations and financial policies using the equity method. All intercompany accounts, transactions and balances have been eliminated in consolidation. Noncontrolling interests in consolidated pass-through entities are recognized before income taxes. The transactions included in net income in the consolidated statements of operations are the same as those that would be presented in comprehensive income. Thus, the Company's net income equates to comprehensive income. The financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. In the opinion of management, these financial statements reflect all adjustments considered necessary to fairly state the results for the interim periods shown, including normal recurring accruals and other items. These financial statements, including the consolidated balance sheet as of September 30, 2019 , which was derived from audited financial statements, do not include all of the information and notes required by GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s annual report on Form 10-K for the fiscal year ended September 30, 2019 . In October 2017 , Forestar became a majority-owned subsidiary of D.R. Horton, Inc. (D.R. Horton) by virtue of a merger with a wholly-owned subsidiary of D.R. Horton. Immediately following the merger, D.R. Horton owned 75% of the Company's outstanding common stock. In connection with the merger, the Company entered into certain agreements with D.R. Horton including a Stockholder’s Agreement, a Master Supply Agreement, and a Shared Services Agreement. D.R. Horton is considered a related party of Forestar under GAAP. At December 31, 2019 , D.R. Horton owned approximately 65% of the Company's outstanding common stock.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Adoption of New Accounting Standard In February 2016, the FASB issued ASU 2016-02, “Leases,” which requires that lease assets and liabilities be recognized on the balance sheet and that key information about leasing arrangements be disclosed. The guidance was effective for the Company beginning October 1, 2019 and did not have a material impact on its consolidated financial position, results of operations or cash flows. As a result of the adoption of this standard on October 1, 2019, the Company recorded right of use assets of $ 2.7 million and lease liabilities of $2.9 million . Lease right of use assets are included in other assets and lease liabilities are included in accrued expenses and other liabilities in the consolidated balance sheet.
New Accounting Pronouncements, Policy [Policy Text Block]	Pending Accounting Standards In December 2019, the FASB issued ASU 2019-12 related to simplifying the accounting for income taxes. The guidance is effective for the Company beginning October 1, 2021, although early adoption is permitted. The Company is currently evaluating the impact of this guidance, and it is not expected to have a material impact on its consolidated financial position, results of operations and cash flows.

Real Estate (Tables)

Real Estate (Tables)	3 Months Ended
	Dec. 31, 2019
Real Estate [Abstract]
Real Estate	Real estate consists of: December 31, September 30, (In millions) Developed and under development projects $ 1,051.4 $ 1,011.8 Undeveloped land 15.4 17.1 $ 1,066.8 $ 1,028.9

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Dec. 31, 2019
Revenues [Abstract]
Revenue from External Customers by Products and Services [Table Text Block]	Revenues consist of: Three Months Ended December 31, 2019 2018 (In millions) Residential lot sales $ 217.1 $ 34.7 Residential tract sales 30.0 — Commercial tract sales — 3.5 Other 0.1 0.3 $ 247.2 $ 38.5

Capitalized Interest (Tables)

Capitalized Interest (Tables)	3 Months Ended
	Dec. 31, 2019
Capitalized Interest [Abstract]
Capitalized Interest Costs [Table Text Block]	The following table summarizes the Company’s interest costs incurred, capitalized and expensed during the three months ended December 31, 2019 and 2018 . Three Months Ended December 31, 2019 2018 (In millions) Capitalized interest, beginning of period $ 23.7 $ 3.2 Interest incurred 9.9 2.8 Interest charged to cost of sales (3.8 ) (0.7 ) Capitalized interest, end of period $ 29.8 $ 5.3

Investment in Unconsolidated _2

Investment in Unconsolidated Ventures (Tables)	3 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Summarized Financial Information	Combined summarized balance sheet and income statement information for these unconsolidated ventures follows: December 31, September 30, (In millions) Assets: Cash and cash equivalents $ 1.4 $ 1.6 Real estate 10.1 13.6 Other assets 0.2 0.1 Total assets $ 11.7 $ 15.3 Liabilities and Equity: Accounts payable and other liabilities $ 0.3 $ 0.3 Equity 11.4 15.0 Total liabilities and equity $ 11.7 $ 15.3 Forestar's investment in unconsolidated ventures $ 5.9 $ 7.3 Three Months Ended December 31, 2019 2018 (In millions) Revenues $ 2.0 $ 1.8 Earnings $ 1.4 $ 1.4 Forestar's equity in earnings of unconsolidated ventures $ 0.5 $ 0.6

Other Assets, Accrued Expense_2

Other Assets, Accrued Expenses and Other Liabilities (Tables)	3 Months Ended
	Dec. 31, 2019
Other Assets, Accrued Expenses and Other Liabilities [Abstract]
Schedule of Other Assets [Table Text Block]	The Company's other assets at December 31, 2019 and September 30, 2019 were as follows: December 31, September 30, (In millions) Receivables, net $ 1.1 $ 1.1 Lease right of use assets 2.7 — Prepaid expenses 2.4 3.4 Land purchase contract deposits 5.0 5.1 Other assets 6.2 4.1 $ 17.4 $ 13.7
Schedule of Accrued Liabilities [Table Text Block]	The Company's accrued expenses and other liabilities at December 31, 2019 and September 30, 2019 were as follows: December 31, September 30, (In millions) Accrued employee compensation and benefits $ 4.9 $ 5.6 Accrued property taxes 1.8 2.1 Accrued interest 7.4 13.5 Contract liabilities 4.0 2.5 Deferred income 9.3 9.3 Accrued development costs 38.9 35.4 Other accrued expenses 10.6 8.4 Other liabilities 5.8 2.8 $ 82.7 $ 79.6

Debt (Tables)

Debt (Tables)	3 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	The Company's notes payable at their principal amounts, net of unamortized discounts and debt issuance costs, consist of the following: December 31, September 30, (In millions) Unsecured: 3.75% convertible senior notes due 2020 $ 118.0 $ 116.7 8.0% senior notes due 2024 344.1 343.8 Revolving credit facility — — $ 462.1 $ 460.5

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements, Not Measured at Fair Value	For the financial assets and liabilities that the Company does not reflect at fair value, the following tables present both their respective carrying value and fair value at December 31, 2019 and September 30, 2019 . Fair Value at December 31, 2019 Carrying Value Level 1 Level 2 Level 3 Total (in millions) Cash and cash equivalents (a) $ 373.3 $ 373.3 $ — $ — $ 373.3 Debt (b) 462.1 — 501.1 — 501.1 Fair Value at September 30, 2019 Carrying Value Level 1 Level 2 Level 3 Total (in millions) Cash and cash equivalents (a) $ 382.8 $ 382.8 $ — $ — $ 382.8 Debt (b) 460.5 — 497.3 — 497.3 _____________________ (a) The fair values of cash and cash equivalents approximate their carrying values due to their short-term nature and are classified as Level 1 within the fair value hierarchy. (b) At December 31, 2019 and September 30, 2019 , debt consisted of the Company's senior and convertible senior notes. The fair value of the senior notes is determined based on quoted prices, which is classified as Level 2 within the fair value hierarchy.

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	3 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Attributable to Common Shareholders and Weighted Average Common Shares Outstanding	The computations of basic and diluted earnings per share are as follows: Three Months Ended December 31, 2019 2018 (In millions, except share data) Numerator: Net income attributable to Forestar Group Inc. $ 16.9 $ 3.3 Denominator: Weighted average common shares outstanding — basic 48,011,132 41,952,493 Dilutive effect of share based compensation 55,286 6,206 Total weighted average shares outstanding — diluted 48,066,418 41,958,699 Anti-dilutive awards excluded from diluted weighted average shares — — Basic net income per common share attributable to Forestar Group Inc. $ 0.35 $ 0.08 Diluted net income per common share attributable to Forestar Group Inc. $ 0.35 $ 0.08

Related Party Transactions Rela

Related Party Transactions Related Party Transactions (Tables)	3 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	At December 31, 2019 and September 30, 2019 , the Company owned or controlled through option purchase contracts approximately 44,500 and 38,300 residential lots, of which D.R. Horton had the following involvement. December 31, September 30, (Dollars in millions) Residential lots under contract to sell to D.R. Horton 12,700 12,800 Residential lots subject to right of first offer with D.R. Horton 12,900 10,600 Earnest money deposits from D.R. Horton for lots under contract $ 87.5 $ 88.7 Remaining purchase price of lots under contract with D.R. Horton $ 918.6 $ 953.8 In the three months ended December 31, 2019 and 2018 , the Company's residential lot sales totaled 2,422 and 518 , and lot sales revenues were $217.1 million and $34.7 million . Lot and land sales to D.R. Horton during those periods were as follows. Three Months Ended December 31, 2019 2018 (Dollars in millions) Residential single-family lots sold to D.R. Horton 2,390 455 Residential lot sales revenues from sales to D.R. Horton $ 215.6 $ 32.6 Residential tract acres sold to D.R. Horton 36 — Residential tract sales revenues from sales to D.R. Horton $ 7.2 $ —

Basis of Presentation Details (

Basis of Presentation Details (Details) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 05, 2017	Oct. 01, 2019	Sep. 30, 2019
Entity Information [Line Items]
Operating Lease, Right-of-Use Asset	$ 2.7		$ 2.7	$ 0
Operating Lease, Liability			$ 2.9
Majority Shareholder [Member] | D.R. Horton, Inc. [Member]
Entity Information [Line Items]
Sale of Stock, Percentage of Ownership after Transaction	65.00%	75.00%

Real Estate - Real Estate (Deta

Real Estate - Real Estate (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Sep. 30, 2019
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Payments to Acquire Residential Real Estate	$ 122.2
Payments to Develop Real Estate Assets	114
Real estate	1,066.8	$ 1,028.9
Developed and under development projects
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Real estate	1,051.4	1,011.8
Land [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Real estate	$ 15.4	$ 17.1
Minimum [Member] | D.R. Horton, Inc. [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Related Party Transaction, Rate	12.00%
Maximum [Member] | D.R. Horton, Inc. [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Related Party Transaction, Rate	16.00%

Revenues (Details)

Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Other	$ 0.1	$ 0.3
Revenue, Net (Deprecated 2018-01-31)	247.2	38.5
Real Estate [Member] | Residential Real Estate [Member]
Revenue from External Customer [Line Items]
Residential lot sales	217.1	34.7
Land [Member] | Residential Real Estate [Member]
Revenue from External Customer [Line Items]
Residential lot sales	30	0
Land [Member] | Commercial Real Estate [Member]
Revenue from External Customer [Line Items]
Residential lot sales	$ 0	$ 3.5

Capitalized Interest (Details)

Capitalized Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Capitalized Interest Costs [Line Items]
Real Estate Inventory, Capitalized Interest Costs	$ 29.8	$ 5.3	$ 23.7	$ 3.2
Interest Costs Incurred	9.9	2.8
Real Estate Inventory, Capitalized Interest Costs, Cost of Sales	$ (3.8)	$ (0.7)

Investment in Unconsolidated _3

Investment in Unconsolidated Ventures - Additional Information (Detail)	Dec. 31, 2019venture
Schedule of Equity Method Investments [Line Items]
Number of ventures under ownership interest using equity method	4

Investment in Unconsolidated _4

Investment in Unconsolidated Ventures - Summarized Balance Sheet Information (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Equity Method Investment, Summarized Financial Information, Assets	$ 11.7	$ 15.3
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Equity Method Investment, Summarized Financial Information, Liabilities and Equity	11.7	15.3
Investment in unconsolidated ventures	5.9	7.3
Cash and cash equivalents
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Equity Method Investment, Summarized Financial Information, Assets	1.4	1.6
Real estate
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Equity Method Investment, Summarized Financial Information, Assets	10.1	13.6
Other assets
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Equity Method Investment, Summarized Financial Information, Assets	0.2	0.1
Accounts Payable and Accrued Liabilities [Member]
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Equity Method Investment, Summarized Financial Information, Liabilities	0.3	0.3
Equity
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Equity Method Investment Summarized Financial Information, Equity	$ 11.4	$ 15

Investment in Unconsolidated _5

Investment in Unconsolidated Ventures - Summarized Income Statement Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Revenues	$ 2	$ 1.8
Earnings (loss)	1.4	1.4
Equity in earnings of unconsolidated ventures	$ 0.5	$ 0.6

Other Assets, Accrued Expense_3

Other Assets, Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 01, 2019	Sep. 30, 2019
Segment Reporting Information [Line Items]
Receivables, net	$ 1.1		$ 1.1
Operating Lease, Right-of-Use Asset	2.7	$ 2.7	0
Prepaid expenses	2.4		3.4
Land purchase contract deposits	5		5.1
Other assets	6.2		4.1
Total Other assets	17.4		13.7
Accrued employee compensation and benefits	4.9		5.6
Accrued property taxes	1.8		2.1
Accrued interest	7.4		13.5
Contract liabilities	4		2.5
Deferred income	9.3		9.3
Accrued Development Costs	38.9		35.4
Other accrued expenses	10.6		8.4
Other liabilities	5.8		2.8
Total Accrued expenses and other liabilities	$ 82.7		$ 79.6

Debt, net - Schedule of Debt (D

Debt, net - Schedule of Debt (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Debt	$ 462.1	$ 460.5
Long-term Line of Credit	0	0
3.75% convertible senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt	$ 118	116.7
Debt Instrument, Maturity Date	Mar. 1, 2020
Interest rate percentage	3.75%
Senior Notes [Member]
Debt Instrument [Line Items]
Debt	$ 344.1	$ 343.8
Debt Instrument, Maturity Date	Apr. 15, 2024
Interest rate percentage	8.00%

Debt, net - Additional Informat

Debt, net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Repayments of Long-term Lines of Credit	$ 0
Line of Credit Facility, Current Borrowing Capacity	380
Line of Credit Facility, Maximum Borrowing Capacity	570
Letter of Credit, Maximum Borrowing Capacity	$ 100
Letter of Credit, Maximum Borrowing Capacity, Percentage of Revolving Credit Commitment	50.00%
Proceeds from Long-term Lines of Credit	$ 0
Long-term Line of Credit	0	$ 0
Line of Credit Facility, Remaining Borrowing Capacity	351.3
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350
Effective interest rate of liability component	8.50%
Interest rate percentage	8.00%
Debt Instrument, Maturity Date	Apr. 15, 2024
Deferred finance costs, net	$ 5.9	6.2
3.75% convertible senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt Instrument, Face Amount	118.9
Debt Instrument, Unamortized Discount	$ 0.8
Effective interest rate of liability component	8.00%
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 16.8
Interest rate percentage	3.75%
Debt Instrument, Maturity Date	Mar. 1, 2020
Deferred finance costs, net	$ 0.1	$ 0.2
Line of Credit [Member]
Debt Instrument [Line Items]
Letters of credit outstanding	$ 28.7

Fair Value Measurements, Not Me

Fair Value Measurements, Not Measured at Fair Value (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 373.3	$ 382.8	$ 170.3	$ 335
Debt	462.1	460.5
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	373.3	382.8
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	501.1	497.3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	0	0
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	373.3	382.8
Long-term Debt, Fair Value	501.1	497.3
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 462.1	$ 460.5

Net Income (Loss) per Share - E

Net Income (Loss) per Share - Earnings Attributable to Common Shareholders and Weighted Average Common Shares Outstanding (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Continuing operations
Net income (loss) attributable to Forestar Group Inc.	$ 16.9	$ 3.3
Denominator:
Weighted average common shares outstanding — basic	48,011,132	41,952,493
Dilutive effect of share based compensation	55,286	6,206
Total weighted average shares outstanding — diluted	48,066,418	41,958,699
Anti-dilutive awards excluded from diluted weighted average shares (in shares)	0	0
Earnings Per Share, Basic	$ 0.35	$ 0.08
Earnings Per Share, Diluted	$ 0.35	$ 0.08

Net Income (Loss) per Share - A

Net Income (Loss) per Share - Additional Information (Detail)	Dec. 31, 2019$ / shares
3.75% convertible senior notes due 2020, net of discount
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion price of convertible notes	$ 51.42

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Income tax expense	$ 5.4	$ 1
Effective income tax rate, percent	24.00%	21.00%
Deferred Tax Assets, Net Of Deferred Tax Liabilities	$ 15.1		$ 20.7
Valuation allowance, deferred tax asset, amount	3.3		$ 3.3
Unrecognized tax benefits	$ 1.3

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares
Class of Stock [Line Items]
Equity Securities Registered, Value	$ 500
Shares Issued, Price Per Share | $ / shares	$ 17.50
Common Stock Available for Issuance, Value Remaining	$ 394.3
Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues | shares	6

Commitments and Contingencies N

Commitments and Contingencies Narrative (Details) $ in Millions	Dec. 31, 2019USD ($)
Loss Contingencies [Line Items]
Special Assessment Bond	$ 170.4
Line of Credit [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount	$ 28.7

Related Party Transactions (Det

Related Party Transactions (Details)	3 Months Ended
	Dec. 31, 2019USD ($)Lot	Dec. 31, 2018USD ($)	Sep. 30, 2019USD ($)Lot
Related Party Transaction [Line Items]
Number of Units in Real Estate Property | Lot	44,500		38,300
Due to Related Parties, Current	$ 2,800,000		$ 2,200,000
Number of Lots Sold	2,422	518
Real estate	$ 1,066,800,000		1,028,900,000
Related Party Transaction, Purchase Obligation from Parent	918,600,000		$ 953,800,000
D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	1,300,000	$ 500,000
Deferred Revenue, Period Increase (Decrease)	(1,500,000)	(3,600,000)
Related Party Transaction, Purchases from Related Party	1,500,000	500,000
General and Administrative Expense [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 600,000	$ 300,000
D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Number of Lots Sold	2,390	455
Revenue from Related Parties	$ 215,600,000	$ 32,600,000
Under Contract [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Number of Units in Real Estate Property | Lot	12,700		12,800
Related Party Deposit Liabilities	$ 87,500,000		$ 88,700,000
Right of First Offer [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Number of Units in Real Estate Property | Lot	12,900		10,600
Land [Member]
Related Party Transaction [Line Items]
Real estate	$ 15,400,000		$ 17,100,000
Other Expense [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	5,200,000	3,000,000
Deposits [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 10,700,000	$ 12,100,000
Land [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Number of Lots Sold	36	0
Revenue from Related Parties	$ 7,200,000	$ 0
Minimum [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Rate	12.00%
Maximum [Member] | D.R. Horton, Inc. [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Rate	16.00%
Real Estate [Member] | Residential Real Estate [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 217,100,000	$ 34,700,000