Statement of Financial Position [Abstract] Short-term investments Short-term Investments Total current assets Operating lease right-of-use assets Total assets Assets Current operating lease liabilities Total current liabilities Long-term operating lease liabilities Total long-term liabilities Total REX shareholders’ equity Total equity Balance Balance Total liabilities and equity Income Statement [Abstract] Gross profit (loss) Gross profit (loss) Segment gross (loss) profit: Income (loss) before income taxes Income (loss) before income taxes: Net income (loss) Net (loss) income Net income (loss) including noncontrolling interests Net income (loss) attributable to REX common shareholders Net income (loss) Weighted average shares outstanding – basic and diluted (in Shares) Basic and diluted net income (loss) per share attributable to REX common shareholders (in Dollars per share) Statement of Stockholders' Equity [Abstract] Balance (in Shares) Balance (in Shares) Equity Components [Axis] Statement of Cash Flows [Abstract] Amortization of operating lease right-of-use assets Net cash provided by (used in) operating activities Net cash used in investing activities Net increase (decrease) in cash, cash equivalents and restricted cash Cash, cash equivalents and restricted cash, beginning of period Cash, cash equivalents and restricted cash, end of period Right-of-use assets acquired and liabilities incurred upon lease execution Condensed Financial Information Disclosure [Abstract] Accounting Policies [Abstract] Schedule of Components of Inventory [Abstract] Ethanol and other finished goods Work in process Grain and other raw materials Total Inventory Revenue from Contract with Customer [Abstract] Disclosure Text Block [Abstract] Schedule of Components of Lease Expense [Abstract] Total lease expense Schedule of Future Minimum Rental Payments for Operating Leases [Abstract] Total Operating lease liabilities Fair Value Disclosures [Abstract] Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract] Investment in cooperative Fair Value Hierarchy and NAV [Axis] Property, Plant and Equipment [Abstract] Schedule of Property and Equipment [Abstract] Total Property and equipment, net Disclosure Text Block Supplement [Abstract] Schedule of Accrued Expenses and Other Current Liabilities [Abstract] Accrued transportation related items Total Derivative Instruments and Hedging Activities Disclosure [Abstract] Schedule of Fair Values for Derivative Financial Instruments [Abstract] Derivative Instrument [Axis] Schedule of Equity Method Investments [Abstract] Schedule of Financial Information For Equity Method Investment [Abstract] Investment, Name [Axis] Schedule of Non-Vested Restricted Stock Award Activity [Abstract] Non-Vested Shares, Beginning of Period Non-Vested Shares, End of Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Weighted Average Grant Date Fair Value, Beginning of Period Weighted Average Grant Date Fair Value, End of Period Income Tax Disclosure [Abstract] Schedule of Unrecognized Tax Benefits Roll Forward [Abstract] Unrecognized tax benefits, beginning of period Unrecognized tax benefits, end of period Commitments and Contingencies Disclosure [Abstract] Related Party Transactions [Abstract] Segment Reporting [Abstract] Schedule Of Segment Results And Assets [Abstract] Segments [Axis] Schedule Of Segment Assets [Abstract] Document Type Document Quarterly Report Document Period End Date Document Fiscal Year Focus Document Transition Report Entity File Number Entity Registrant Name Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address, State or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Security Exchange Name Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Amendment Flag Current Fiscal Year End Date Document Fiscal Period Focus Entity Central Index Key Assets: Current assets: Cash and cash equivalents Restricted cash Accounts receivable Refundable income taxes Prepaid expenses and other Deferred taxes and other assets Equity method investment Big River Liabilities and equity: Current liabilities: Accounts payable, trade (includes $1.3 million and $0.7 million with related parties at April 30, 2021 and January 31, 2021, respectively) Accounts payable, related parties Accounts Payable, Related Parties, Current Accrued expenses and other current liabilities (includes $0.1 million with related parties at April 30, 2021 and January 31, 2021) Accrued expenses, related parties Long-term liabilities: Deferred taxes Other long-term liabilities Equity: REX shareholders’ equity: Common stock Paid-in capital Retained earnings Noncontrolling interests Net sales and revenue Cost of sales (includes $16.7 million and $12.3 million with related parties for the quarters ended April 30, 2021 and 2020, respectively) Cost of sales, related parties Equity in income (loss) of unconsolidated affiliates (Income) loss from equity method investments Interest and other income, (net) Capital contributions Capital contributions from minority investor Issuance of equity awards and stock based compensation expense Treasury stock acquired (in Shares) Cash flows from operating activities: Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Depreciation Dividends received from equity method investee Proceeds from Equity Method Investment, Distribution Deferred income tax Stock based compensation expense Changes in assets and liabilities: Accounts payable, trade Other liabilities Cash flows from investing activities: Maturities of short-term investments Cash flows from financing activities: Payments to noncontrolling interests holders Net cash used in financing activities Non cash investing activities – Accrued capital expenditures Non cash financing activities – Stock awards accrued Reconciliation of total cash, cash equivalents and restricted cash: Treasury stock Selling, general and administrative expenses (includes $(0.3) million with related parties for the quarter ended April 30, 2020) Selling, general and administrative expenses, related parties (Provision) benefit for income taxes (Provision) benefit for income taxes: Net (income) loss attributable to noncontrolling interests Noncontrolling interests distribution and other Treasury stock acquired Interest income from investments Gain on sale of property and equipment – net Accounts receivable Inventories Other assets Capital expenditures Purchases of short-term investments Other Treasury stock acquired Common Stock [Member] Treasury Stock [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Noncontrolling Interest [Member] Condensed Financial Information of Parent Company Only Disclosure [Text Block] Significant Accounting Policies [Text Block] Schedule of Inventory, Current [Table Text Block] Revenue from Contract with Customer [Text Block] Leases of Lessee Disclosure [Text Block] Lease, Cost [Table Text Block] Operating lease expense Variable lease expense Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] 2022 2023 2024 2025 2026