Subsequent Event [Abstract] Subsequent Event [Abstract] Subsequent Event Subsequent Events [Text Block] Accounting Policies [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2015-03 Accounting Standards Update 2015-03 [Member] Accounting Standards Update 2015-03 [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets Other Assets [Member] Long-term Debt Long-term Debt [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Deferred finance costs, net Deferred Finance Costs, Net Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Estimate of Fair Value Measurement Estimate of Fair Value Measurement [Member] Reported Value Measurement Reported Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fixed rate debt Long-term Debt, Fair Value Equity Method Investments and Joint Ventures [Abstract] Summarized Balance Sheet Information Summarized Equity Method Investments Balance Sheet Information Table [Text Block] Summarized balance sheet information for equity method joint ventures. Summarized Income Statement Information Summarized Equity Method Investments Income Statement Information Table [Text Block] Summarized income statement information for equity method joint ventures. Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Real estate, net Inventory, Real Estate, Land and Land Development Costs Oil and gas properties and equipment, net Oil and Gas Property, Successful Effort Method, Net Assets held for sale Disposal Group, Including Discontinued Operation, Assets Investment in unconsolidated ventures Equity Method Investments Timber Timber and Timberlands Receivables, net Accounts and Notes Receivable, Net Income taxes receivable Income Taxes Receivable Prepaid expenses Prepaid Expense Property and equipment, net Property, Plant and Equipment, Net Goodwill and other intangible assets Intangible Assets, Net (Including Goodwill) Other assets Other Assets TOTAL ASSETS Assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Accounts payable Accounts Payable Accrued employee compensation and benefits Employee-related Liabilities Accrued property taxes Accrual for Taxes Other than Income Taxes Accrued interest Interest Payable Deferred tax liability, net Deferred Tax Liabilities, Net Earnest money deposits Customer Advances and Deposits Other accrued expenses Other Accrued Liabilities Liabilities held for sale Disposal Group, Including Discontinued Operation, Liabilities Other liabilities Other Liabilities Debt Long-term Debt TOTAL LIABILITIES Liabilities COMMITMENTS AND CONTINGENCIES Commitments and Contingencies EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Forestar Group Inc. shareholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, par value $1.00 per share, 200,000,000 authorized shares, 36,946,603 issued at first quarter-end 2016 and year-end 2015 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings (Accumulated deficit) Retained Earnings (Accumulated Deficit) Treasury stock, at cost, 3,038,601 shares at first quarter-end 2016 and 3,203,768 shares at year-end 2015 Treasury Stock, Value Total Forestar Group Inc. shareholders’ equity Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest TOTAL EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest TOTAL LIABILITIES AND EQUITY Liabilities and Equity Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Items not allocated to segments Corporate, Non-Segment [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Real estate Real Estate Segment [Member] Real Estate Segment [Member] Oil and Gas Oil And Gas [Member] Oil And Gas [Member] Other natural resources Other Natural Resources [Member] Other Natural Resources [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Total Assets Assets Allocated by Segment Reconciliation of Assets from Segment to Consolidated [Table Text Block] Segment Revenues and Earnings Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill Goodwill Identified intangibles, net Intangible Assets, Net (Excluding Goodwill) Goodwill and other intangible assets Extractive Industries [Abstract] Oil and Gas Properties Oil and Gas Properties [Text Block] Subsequent Event [Table] Subsequent Event [Table] Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] Eleven Eleven [Member] Eleven [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Not Discontinued Operations Disposal Group, Not Discontinued Operations [Member] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Radisson Hotel & Suites, Austin Radisson Hotel & Suites, Austin [Member] Radisson Hotel & Suites, Austin [Member] Bakken/Three Forks Oil and Gas Properties Bakken/Three Forks Oil and Gas Properties [Member] Bakken/Three Forks Oil and Gas Properties [Member] Real Estate Property Ownership [Axis] Real Estate Property Ownership [Axis] Real Estate Properties [Domain] Real Estate Properties [Domain] Multi Family Property Multi Family Property [Member] Multifamily property. Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Austin, Texas Austin Texas [Member] Austin, Texas. Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Number of units of multifamily project Number of Units in Real Estate Property Purchase price of properties sold Disposal Group, Including Discontinued Operation, Consideration Net proceeds Proceeds from Sale of Real Estate Payment of debt Repayments of Long-term Debt Debt Disclosure [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Senior Secured Credit Facility Senior Secured Credit Facility [Member] Senior secured credit facility. Convertible Debt Convertible Debt [Member] Six Percent Tangible Equity Units 6% Tangible Equity Units [Member] 6% Tangible Equity Units [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Secured Debt Secured Debt [Member] Other indebtedness Other Debt Obligations [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Interest rate percentage Debt Instrument, Interest Rate, Stated Percentage Deferred finance costs, net Average interest rate Long-term Debt, Weighted Average Interest Rate Variable and fixed interest rates ranging, minimum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum Variable and fixed interest rates ranging, maximum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum Debt instrument, maturity date Debt Instrument, Maturity Date Real Estate [Abstract] SEC Schedule III, Real Estate and Accumulated Depreciation, by Property [Table] SEC Schedule III, Real Estate and Accumulated Depreciation, by Property [Table] Radisson Hotel Radisson Hotel [Member] Radisson Hotel [Member] Undeveloped land (includes land in entitlement) Undeveloped land (includes land in entitlement) [Member] [Member] Entitled, developed and under development projects [Member] [Member] Entitled, developed and under development projects Entitled, developed and under development projects [Member] Entitled, developed and under development projects [Member] West Austin West Austin [Member] West Austin [Member] Downtown Edge Downtown Edge [Member] Downtown Edge [Member] Music Row Music Row [Member] Music Row [Member] Dillon Dillon [Member] Dillon [Member] SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] Carrying value Real Estate Investment Property, at Cost Less: accumulated depreciation SEC Schedule III, Real Estate Accumulated Depreciation Net carrying value Real Estate Investment Property, Net Total Real Estate ScheduleOfGoodwillAndOtherIntangibleAssets [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Credo Credo [Member] Credo Petroleum Corporation [Member] Water Resource Company Water Resource Company [Member] Water Resource Company [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Patents Patents [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Indefinite-lived intangible assets (excluding goodwill) Indefinite-Lived Intangible Assets (Excluding Goodwill) Finite-lived intangible assets, net Finite-Lived Intangible Assets, Net Equity [Abstract] Equity Stockholders' Equity Note Disclosure [Text Block] Real Estate Schedule of Real Estate Properties [Table Text Block] Real Estate Real Estate Disclosure [Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Variable Interest Entities Variable Interest Entities [Text Block] Variable interest entities. Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Receivables [Abstract] Receivables Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Number of business segments Number of Reportable Segments Number of customer who contributed more than 10 percent of revenue Entity Wide Revenue Major Customer Number Entity wide revenue major customer number. Maximum percentage of revenue from customer Concentration Risk, Percentage Segment Information Segment Reporting Disclosure [Text Block] Receivables Loans, Notes, Trade and Other Receivables Disclosure [Text Block] New and Pending Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Number of units of multifamily project Number Of Units Of Multifamily Project Number of units of multifamily project. Goodwill and Other Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] New and Pending Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Segment Earnings Segment Reconciling Items Segment Reconciling Items [Member] Total revenues Revenue, Net Segment reporting information income (loss) from continuing operations before income taxes attributable to parent Income (Loss) from Continuing Operations before Income Taxes Attributable to Parent Income (Loss) from Continuing Operations before Income Taxes Attributable to Parent General and administrative expense General and Administrative Expense Shared-based and long-term incentive compensation expense Allocated Share-based Compensation Expense Interest expense Interest Expense Other corporate non-operating income Other Nonoperating Income Gain (loss) on disposition of proved property Gain (Loss) on Disposition of Proved Property Net mineral acres leased from others sold Net Mineral Acres Leased From Others Sold Net Mineral Acres Leased From Others Sold Gross producing oil and gas wells sold Gross Producing Oil and Gas Wells Sold Gross Producing Oil and Gas Wells Sold Net producing oil and gas wells sold Net Producing Oil and Gas Wells Sold Net Producing Oil and Gas Wells Sold Proceeds from sale of oil and gas property and equipment Proceeds from Sale of Oil and Gas Property and Equipment Reimbursement of capital costs related to sale of in progress wells Reimbursement of Capital Costs Related To Sale of In Progress Wells Reimbursement of Capital Costs Related To Sale of In Progress Wells Loss related to write-off of allocated goodwill Goodwill, Written off Related to Sale of Business Unit Earnings Per Share [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Debt and equity instruments, shares to be Issued Debt And Equity Instruments, shares to be Issued Represents the shares to be issued for our debt and equity instruments Conversion price of convertible notes Debt Instrument, Convertible, Conversion Price Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Current Maturities of Borrowings Other Current Liabilities [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Number of primary beneficiary Count of VIEs Count of Variable Interest Entities Total assets of developed and under developed real estate Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets Total liabilities of developed and under developed real estate Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities Investment in VIEs Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net Contributed to VIE Variable Interest Entity, Financial or Other Support, Amount Maximum Exposure to loss related to VIEs Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Statement of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Consolidated net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation, depletion and amortization Depreciation, Depletion and Amortization Change in deferred income taxes Increase (Decrease) in Deferred Income Taxes Equity in earnings of unconsolidated ventures Income (Loss) from Equity Method Investments Distributions of earnings of unconsolidated ventures Proceeds from Equity Method Investment, Dividends or Distributions Share-based compensation Share-based Compensation Real estate cost of sales Real Estate Cost Of Sales Real Estate Cost Of Sales Dry hole and unproved leasehold impairment charges Exploration Abandonment and Impairment Expense Real estate development and acquisition expenditures, net Payments to Acquire and Develop Real Estate Reimbursements from utility and improvement districts Recovery of Direct Costs Gain on sale of assets Gain (Loss) on Disposition of Assets Other Other Noncash Income (Expense) Changes in: Increase (Decrease) in Operating Capital [Abstract] Notes and accounts receivable Increase (Decrease) in Accounts and Notes Receivable Prepaid expenses and other Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable and other accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Income taxes Increase (Decrease) in Income Taxes Payable Net cash provided by (used for) operating activities Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities [Abstract] Property, equipment, software, reforestation and other Payments to Acquire Productive Assets Oil and gas properties and equipment Payments to Acquire Oil and Gas Property and Equipment Investment in unconsolidated ventures Payments to Acquire Equity Method Investments Proceeds from sales of assets Proceeds from Sales of Assets, Investing Activities Return of investment in unconsolidated ventures Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Net cash provided by (used for) investing activities Net Cash Provided by (Used in) Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Payments of debt Additions to debt Proceeds from Issuance of Long-term Debt Deferred financing fees Payments of Financing Costs Distributions to noncontrolling interests, net Payments to Noncontrolling Interests Exercise of stock options Proceeds from Stock Options Exercised Payroll taxes on issuance of stock-based awards Payments Related to Tax Withholding for Share-based Compensation Excess income tax benefit from share-based compensation Excess Tax Benefit from Share-based Compensation, Financing Activities Net cash provided by (used for) financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Carrying value of goodwill and other intangible assets Schedule of Intangible Assets and Goodwill [Table Text Block] Earnings Attributable to Common Shareholders and Weighted Average Common Shares Outstanding Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] General and administrative expense General and Administrative Expense [Member] Other Operating Expenses Other Operating Expenses [Member] Other Operating Expenses [Member] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Share based and Long Term Incentive Compensation Share-Based and Long-Term Incentive Compensation Share Based and Long Term Incentive Compensation Effective income tax rate reconciliation, percent Effective Income Tax Rate Reconciliation, Percent Benefit due to change in valuation allowance (as a percent) Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Detriment for goodwill due to the sale of oil and gas assets (as a percent) Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Percent Benefit for noncontrolling interests (as a percent) Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent Detriment for share-based compensation benefits that will not be realized (as a percent) Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Valuation allowance, deferred tax asset, amount Deferred Tax Assets, Valuation Allowance Commitments and Contingencies Disclosure [Abstract] Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Severance Costs Special Termination Benefits [Member] Retention Bonuses Facility Closing [Member] Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] Restructuring Reserve Restructuring Reserve Restructuring charges Restructuring Charges Payments for restructuring Payments for Restructuring Restructuring Reserve Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Real Estate Real Estate [Member] Proved Oil Gas Property ProvedOilGasProperty [Member] ProvedOilGasProperty [Member] Oil and Gas Properties Oil and Gas Properties [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Nonrecurring Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Assets, fair value disclosure, nonrecurring Assets, Fair Value Disclosure, Nonrecurring Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Equity Method Investments Equity Method Investments [Member] Non-recourse Debt Non-recourse Debt [Member] Non-recourse Debt [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Long-term debt, current maturities Long-term Debt, Current Maturities Equity method investment, deferred gain on sale Equity Method Investment, Deferred Gain on Sale Unrecognized basis difference on equity method investment Equity Method Investment, Difference Between Carrying Amount and Underlying Equity Debt Schedule of Long-term Debt Instruments [Table Text Block] Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Equity [Table] Equity [Table] Equity [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Employees of former affliate Former Affiliated Entity [Member] Former Affiliated Entity, Temple Inland [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Employee Stock Option Employee Stock Option [Member] Equity [Line Items] Equity [Line Items] Equity [Line Items] Options to purchase shares of common stock Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted average exercise price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Exercisable at end of period, weighted average remaining contractual term (less than) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] 242, LLC Two Hundred Forty Two Llc [Member] 242, LLC. CL Ashton Woods Cl Ashton Woods [Member] CL Ashton Woods. CL Realty CL Realty [Member] CL Realty. CREA FMF CREA FMF [Member] CREA FMF [Member] Elan 99, LLC Elan 99, LLC [Member] Elan 99, LLC [Member] FMF Littleton FMF Littleton [Member] FMF Littleton multifamily project in Littleton, Colorado FMF Peakview Fmf Peakview Llc [Member] FMF Peakview LLC. FOR/SR Forsyth LLC FOR/SR Forsyth LLC [Member] FOR/SR Forsyth LLC [Member] HM Stonewall Estates Hm Stonewall Estates [Member] HM Stonewall Estates. LM Land Holdings Lm Land Holdings [Member] LM Land Holdings. MRECV DT Holdings LLC MRECV DT Holdings LLC [Member] MRECV DT Holdings LLC [Member] MRECV Edelweiss LLC MRECV Edelweiss LLC [Member] MRECV Edelweiss LLC [Member] MREC VH Juniper Ridge LLC MRECV Juniper Ridge LLC [Member] MRECV Juniper Ridge LLC [Member] MRECV Meadow Crossing II LLC MRECV Meadow Crossing II LLC [Member] MRECV Meadow Crossing II LLC Miramonte Boulder Pass, LLC Miramonte Boulder Pass, LLC [Member] [Domain] Miramonte Boulder Pass, LLC [Member] PSW Communities PSW Communities [Member] PSW Communities [Member] Temco Temco [Member] Temco. Other ventures Other Ventures [Member] Other ventures. Revenues Equity Method Investment, Summarized Financial Information, Revenue Earnings (loss) Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations before Extraordinary Items Equity in earnings of unconsolidated ventures Earnings available to common shareholders: Net Income (Loss) Attributable to Parent [Abstract] Less: Net (income) loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Earnings (loss) available for diluted earnings per share Net Income (Loss) Attributable to Parent Less: Undistributed net income allocated to participating securities Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Earnings (loss) available to common shareholders for basic earnings per share Net Income (Loss) Available to Common Stockholders, Basic Weighted average common shares outstanding - basic Weighted Average Number of Shares Outstanding, Basic Weighted average common shares upon conversion of participating securities Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements Dilutive effect of stock options, restricted stock and equity-settled awards Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average common shares outstanding - diluted Weighted Average Number of Shares Outstanding, Diluted Anti-dilutive awards excluded from diluted weighted average shares Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule of Real Estate Properties [Table] Schedule of Real Estate Properties [Table] San Antonio Texas San Antonio Texas [Member] San Antonio Texas. Utility and Improvement District [Member] Utility And Improvement District [Member] Utility and improvement district. Cibolo Canyons Project Cibolo Canyons Project [Member] Cibolo canyons project. Real Estate Properties [Line Items] Real Estate Properties [Line Items] Real estate property sale price Real Estate Property Sale Price Real Estate Property Sale Price Gain on sale of assets Real estate assets held for sale Real Estate Held-for-sale Cost of asset in developed and under development projects Cost Of Asset In Entitled Developed And Under Development Projects Cost of asset in entitled developed and under development projects. Reimbursements from utility and improvement districts Cumulative reimbursable cost associated with real estate projects in development Cumulative Reimbursable Cost Associated With Real Estate Projects In Development Cumulative Reimbursable Cost Associated With Real Estate Projects In Development Return of reimbursements received in relation to direct costs and expenses previously paid or incurred for development of real estate projects Return of reimbursements received in relation to direct costs and expenses previously paid or incurred for development of real estate projects Return of reimbursements received in relation to direct costs and expenses previously paid or incurred for development of real estate projects Components of Share-Based Compensation Expense (Income) Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Share-Based Compensation Expense (Income) Included in Operating Expense Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Discontinued Operations and Disposal Groups [Abstract] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Assets Held for Sale: Assets Held for Sale [Abstract] Assets Held for Sale [Abstract] Real estate, net of accumulated depreciation of $32,945 Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Oil and gas properties and equipment, net of accumulated depletion of $1,162 Prepaid expenses Disposal Group, Including Discontinued Operation, Prepaid and Other Assets Goodwill and other intangible assets Disposal Group, Including Discontinued Operation, Goodwill and Intangible Assets Disposal Group, Including Discontinued Operation, Goodwill and Intangible Assets Liabilities Held for Sale: Liabilities Held For Sale [Abstract] Liabilities Held For Sale [Abstract] Other accrued expenses Disposal Group, Including Discontinued Operation, Accrued Liabilities Other liabilities Disposal Group, Including Discontinued Operation, Other Liabilities Liabilities held for sale Accumulated depletion, held-for-sale properties Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Charlotte, North Carolina Charlotte North Carolina [Member] Charlotte North Carolina [Member] Income Statement [Abstract] REVENUES Revenue, Net [Abstract] Real estate sales and other Sales of Real Estate Commercial and income producing properties Commercial And Income Producing Properties Revenue Commercial And Income Producing Properties Revenue Real estate Real Estate Revenue, Net Oil and gas Oil and Gas Revenue Other natural resources Other Revenue, Net Total revenues COSTS AND EXPENSES Costs and Expenses [Abstract] Cost of real estate sales and other Cost of Real Estate Sales Cost of commercial and income producing properties Cost Of Commercial And Income Producing Properties Cost of commercial and income producing properties. Cost of oil and gas producing activities Oil and Gas Production Expense Cost of other natural resources Other Cost of Operating Revenue Other operating Other Cost and Expense, Operating General and administrative Total expenses Costs and Expenses GAIN ON SALE OF ASSETS OPERATING INCOME (LOSS) Operating Income (Loss) Interest expense Other non-operating income INCOME (LOSS) BEFORE TAXES Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax benefit Income Tax Expense (Benefit) CONSOLIDATED NET INCOME (LOSS) NET INCOME (LOSS) ATTRIBUTABLE TO FORESTAR GROUP INC. WEIGHTED AVERAGE COMMON SHARES OUTSTANDING Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Diluted (in shares) NET INCOME (LOSS) PER COMMON SHARE Basic (usd per share) Earnings Per Share, Basic Diluted (usd per share) Earnings Per Share, Diluted TOTAL COMPREHENSIVE INCOME (LOSS) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Document Document And Entity Information [Abstract] Document Document and Entity Information [Abstract] Statement [Table] Statement [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Statement [Line Items] Statement [Line Items] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Restructuring and Related Costs Restructuring and Related Costs [Table Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Scenario, Forecast Scenario, Forecast [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Base Rate Base Rate [Member] 30 day LIBOR rate Thirty Day LIBOR Rate [Member] Thirty Day LIBOR Rate [Member] Letter of Credit Letter of Credit [Member] Multi Family Development Properties Multi Family Development Properties [Member] Multi Family Development Properties [Member] - This represents other multifamily development properties. Interest coverage ratio Debt Instrument, Covenant, Interest Coverage Ratio Debt Instrument, Covenant, Interest Coverage Ratio Maximum borrowing capacity under term Loan facility Line of Credit Facility, Maximum Borrowing Capacity Maturity period of revolving line of credit Line of Credit Facility, Expiration Date Line of credit facility, letters of credit sublimit Line Of Credit Facility Letters Of Credit Sublimit Line Of Credit Facility Letters Of Credit Sublimit Sublimit for letters of credit outstanding Letters of Credit Outstanding, Amount Net unused borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Debt instrument, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Percentage of variable spread on base rate Percentage Of Variable Spread On Base Rate Percentage Of Variable Spread On Base Rate Percentage of spread on federal funds effective rate Percentage Of Spread On Federal Funds Effective Rate Percentage Of Spread On Federal Funds Effective Rate Minimum net worth required for compliance Minimum Net Worth Required for Compliance Minimum net worth required for compliance (as a percent) Percentage of Net Proceeds Received From Equity Offerings For Net Worth Compliance Percentage of Net Proceeds Received From Equity Offerings For Net Worth Compliance Positive net income requirement for net worth compliance (as a percent) Positive Net Income Percentage Requirement for Net Worth Compliance Positive Net Income Percentage Requirement for Net Worth Compliance Effective leverage ratio (less than) Debt Instrument, Effective Leverage Ratio Debt Instrument, Effective Leverage Ratio Stockholders distribution covenant, interest coverage ratio Debt Instrument, Stockholders Distribution Covenant, Interest Coverage Ratio Debt Instrument, Stockholders Distribution Covenant, Interest Coverage Ratio Minimum liquidity required by covenant Debt Instrument, Covenant, Minimum Liquidity Debt Instrument, Covenant, Minimum Liquidity Payments of capital distribution Payments of Capital Distribution Percentage from sales of properties and non-core assets Debt Instrument, Distribution Funding, Percentage From Sales of Properties and Non-core Assets Debt Instrument, Distribution Funding, Percentage From Sales of Properties and Non-core Assets Principal amount of debt Debt Instrument, Face Amount Redemption price, percentage Debt Instrument, Redemption Price, Percentage Gain on extinguishment of debt Gains (Losses) on Extinguishment of Debt Unamortized debt issuance cost Write off of Deferred Debt Issuance Cost Guest room hotel Number Of Guest Room Number of guest room. Carrying value of multifamily project to secure non recourse loan Carrying Value Of Multifamily Project To Secure Non Recourse Loan Carrying Value of multifamily project to secure Non-recourse loan. Amortization of deferred financing fees Amortization of Financing Costs Fair Value Measurements, Nonrecurring Fair Value Measurements, Nonrecurring [Table Text Block] Information About Our Fixed Rate Financial Instruments Not Measured at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Deferred Bonus and Profit Sharing Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Deferred Bonus and Profit Sharing Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Deferred Bonus and Profit Sharing Arrangement, Individual Contract, Type of Deferred Compensation [Domain] Deferred Bonus and Profit Sharing Arrangement, Individual Contract, Type of Deferred Compensation [Domain] Long-Term Incentive Compensation Long-Term Incentive Compensation [Member] Long-Term Incentive Compensation [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Board of Directors Director [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] First anniversary Share-based Compensation Award, Tranche One [Member] Second anniversary Share-based Compensation Award, Tranche Two [Member] Third anniversary Share-based Compensation Award, Tranche Three [Member] Equity-settled awards Equity Settled Awards [Member] Equity settled awards. Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Granted, equivalent units Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Number of new directors Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Number of Recipients Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Number of Recipients Vesting, number (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number Option term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Compensation expense Deferred Compensation Arrangement with Individual, Compensation Expense Fair value of awards granted to retirement eligible employees and expensed at date of grant Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost Unrecognized share-based compensation expense related to non-vested equity-settled awards, restricted stock and stock options Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Shares issued out of treasury stock Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Shares withheld for payroll taxes Shares Paid for Tax Withholding for Share Based Compensation Value of shares withheld for payroll taxes Deferred compensation arrangement with individual, cash award granted, amount Deferred Compensation Arrangement with Individual, Cash Award Granted, Amount Deferred compensation arrangement with individual, service period (in years) Deferred Compensation Arrangement with Individual, Requisite Service Period Deferred compensation cash-based arrangements, liability, current and noncurrent Deferred Compensation Cash-based Arrangements, Liability, Current and Noncurrent Assets and Liabilities of Properties Held for Sale Assets and Liabilities of Properties Held for Sale [Table Text Block] Assets and Liabilities of Properties Held for Sale [Table Text Block] Net Income per Share Earnings Per Share [Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Receivable Type [Axis] Receivable Type [Axis] Receivable Type [Domain] Receivable [Domain] Funds held by qualified intermediary Funds held by qualified intermediary [Member] Funds held by qualified intermediary [Member] Oil and gas revenue accrual receivable Oil and gas revenue accrual receivable [Member] Oil and gas revenue accrual receivable [Member] Receivables and accrued interest Other Receivables And Accrued Interest [Member] Other receivables and accrued interest. Notes receivable Notes Receivable [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Average interest rates Average Interest Rates Average interest rates. Total Accounts And Notes Receivable Gross Accounts and notes receivable gross. Oil and gas joint interest billing receivables Oil and Gas Joint Interest Billing Receivables Allowance for bad debts Allowance for Doubtful Accounts Receivable Receivables, net Number of ventures under ownership interest using equity method Number of Real Estate Properties Investment in unconsolidated ventures Distributions of return on investments and earnings Distributions Of Return On Investments And Earnings Distributions of return on investments and earnings. Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits, by Title of Individual and by Type of Deferred Compensation [Table] Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits, by Title of Individual and by Type of Deferred Compensation [Table] Other Liabilities Other Liabilities [Member] General and Administrative Expense One-time Termination Benefits One-time Termination Benefits [Member] Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] Area for which certificate of completion received Acres For Which Certificate Of Completion Received Acres for which certificate of completion received. Portion of site for which certificate not received Portion Of Site For Which Certificate Not Received Portion of site for which certificate not received. Accrual for environmental loss contingencies Accrual for Environmental Loss Contingencies, Increase (Decrease) for Revision in Estimates Cost to complete remediation activities Environmental Exit Costs, Costs Accrued to Date Asset retirement obligation Asset Retirement Obligation Restructuring charges Common stock, par value Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Treasury stock, common shares Treasury Stock, Shares Venture Assets Equity Method Investment, Summarized Financial Information, Assets Venture Borrowings Equity Method Investment Summarized Financial Information Borrowing Equity method investment, summarized financial information, borrowing. Venture Equity Equity Method Investment Summarized Financial Information, Equity Investment in venture Debt Debt Disclosure [Text Block] Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table] Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table] Cash Settled Awards Cash Settled Awards [Member] Share-based Compensation Awards, including Restricted Stock Units (RSU/Cs) and Stock Appreciations Rights (SARs), which are to be settled in cash. Restricted Stock Restricted Stock [Member] Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] Total share-based compensation Share based and Long Term Incentive Compensation Reconciliation of Changes in Equity Schedule of Stockholders Equity [Table Text Block] Share-Based Compensation and Long-Term Incentive Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Held for Sale Held For Sale [Text Block] Assets and Liabilities Held For Sale [Text Block] Unproved leasehold interests Unproved Oil and Gas Property, Successful Effort Method Proved oil and gas properties Proved Oil and Gas Property, Successful Effort Method Total costs Capitalized Costs, Oil and Gas Producing Activities, Gross Less: accumulated depreciation, depletion and amortization Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization Net capitalized costs Net Capitalized Costs Related to Oil and Gas Producing Activities Capitalized Costs Relating to Oil and Gas Producing Activities Disclosure [Table Text Block] Fair Value Fair Value Disclosures [Text Block] Investment in Unconsolidated Ventures Equity Method Investments and Joint Ventures Disclosure [Text Block] Noncontrolling Interest [Table] Noncontrolling Interest [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Forestar Group Inc. Parent [Member] Noncontrolling Interest Noncontrolling Interest [Member] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Other (primarily share-based compensation) Adjustments to Additional Paid in Capital, Other Ending balance Area of land Area of Land Due period of notes receivable as secured by deed of trust Due Period Of Notes Receivable As Secured By Deed Of Trust Due period of notes receivable as secured by a deed of trust. Capital Stock Capital Stock [Text Block] Capital Stock