Other cash flow information: Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Customer [Domain] Customer [Domain] Joint Pension Fund Local Union Number 102 IBEW [Member] [Domain] Joint Pension Fund Local Union Number One Zero Two [Member] [Domain] [Domain] for Joint Pension Fund Local Union Number One Zero Two Boilermaker-Blacksmith National Pension Trust [Member] Boilermaker Blacksmith National Pension Trust [Member] Boilermaker blacksmith national pension trust. Shares vested and released Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period State Current State and Local Tax Expense (Benefit) Reconciliation between the expected income tax provision applying the domestic federal statutory tax rate and the reported income tax provision Effective Income Tax Rate Reconciliation, Amount [Abstract] Canadian Prime Rate [Member] Canadian Prime Rate [Member] Canadian Prime Rate [Member] Preferred stock shares outstanding Preferred Stock, Shares Outstanding Costs and estimated earnings in excess of billings on uncompleted contracts Increase (Decrease) in Contract with Customer, Asset Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information Disclosure [Abstract] Foreign currency translation adjustments, tax effect Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Weighted average grant date fair value per share cancelled Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Contract with Customer, Asset and Liability [Table Text Block] Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Customer Three [Member] Customer Three [Member] Customer three. Vest in 2017 [Member] Vest in 2017 [Member] Vest in 2017 [Member] Weighted-average remaining lease term (in years) Operating Lease, Weighted Average Remaining Lease Term Foreign Currency Foreign Currency Transactions and Translations Policy [Policy 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] Share available for grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Incremental intangible amortization expense Business Acquisition, Pro Forma Amortization of Intangible Assets Business Acquisition, Pro Forma Amortization of Intangible Assets Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Income Tax Authority, Description [Axis] Income Tax Authority, Description [Axis] Income Tax Authority: State, Federal and Foreign Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Total intrinsic value of stock option Aggregate intrinsic value exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Tax Credit Carryforward [Line Items] Tax Credit Carryforward [Line Items] Document Fiscal Year Focus Document Fiscal Year Focus Charged to Costs and Expenses SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Storage and Terminal Solutions Segment mtrx:StorageandTerminalSolutionsSegment Storage and Terminal Solutions Segment Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Amortization expense Amortization of Intangible Assets Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Income Tax Authority, Description [Domain] Income Tax Authority, Description [Domain] [Domain] for Income Tax Authority: State, Federal and Foreign Net deferred tax asset Deferred Tax Assets, Net Antidilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Weighted-average discount rate Operating Lease, Weighted Average Discount Rate, Percent Contract with Customer, Liability, Revenue Recognized Contract with Customer, Liability, Revenue Recognized Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Business Acquisition [Axis] Business Acquisition [Axis] Accounts Receivable Reserve - 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Diluted EPS: Earnings Per Share, Diluted [Abstract] Valuation and Qualifying Accounts SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Entity Current Reporting Status Entity Current Reporting Status Percentage of employee contribution for first half Percentage Of Employee Contribution As Base For Employer Contributions Percentage of employee contribution as base for employer contributions. Net deferred tax liability Deferred Tax Liabilities, Net Other Other Noncash Income (Expense) Tax over book depreciation Deferred Tax Liabilities, Property, Plant and Equipment Additional Margin on alternate base rate loans, Maximum Line Of Credit Basis Spread On Alternate Base Rate Maximum Line Of Credit Basis Spread On Alternate Base Rate Maximum Line of credit basis spread on alternate base rate maximum. 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Leverage Ratio, Minimum Senior Leverage Ratio Minimum Senior leverage ratio minimum. Prior credit agreement highest margin Prior Credit Agreement Highest Margin Prior Credit Agreement Highest Margin June 30, 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Four Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Economic purchase price Economicpurchaseprice Purchase price paid at closing including debt assumed, settlement of other liabilities, less cash acquired and customary working capital closing adjustments. Income taxes receivable Income Taxes Receivable, Current Change in costs and estimated earnings in excess of billings on uncompleted contracts Change in CIE Change in CIE from prior year to the current period. Liability for Uncertain Tax Positions, Noncurrent Liability for Uncertainty in Income Taxes, Noncurrent Income Tax Authority [Domain] Income Tax Authority [Domain] Minimum EBITDA Balance Under Covenant Relief Period mtrx:MinimumEBITDABalanceUnderCovenantReliefPeriod Minimum EBITDA Balance Under Covenant Relief Period Summary of Operating Loss Carryforwards Summary of Operating Loss Carryforwards [Table Text Block] Restructuring Reserve Restructuring Reserve Total stockholders' equity before treasury stock Stockholders' Equity before Treasury Stock Trading Symbol Trading Symbol Deferred income taxes Deferred income tax assets Deferred Income Tax Assets, Net Current liabilities: Liabilities, Current [Abstract] Percentage of real estate leases Percentage of real estate leases Percentage of real estate leases Operating Loss Carryforwards, Valuation Allowance Operating Loss Carryforwards, Valuation Allowance Common stock, shares outstanding Shares, Outstanding Stock Issued During Period, Value, Restricted Stock Award, Gross Stock Issued During Period, Value, Restricted Stock Award, Gross Weighted average exercise price exercisable at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Pro-rate of original awards maximum Payout As Percentage Of Original Award Maximum Payout as percentage of original award maximum. Accounting Policies [Abstract] Accounting Policies [Abstract] Weighted average remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Net present value of future lease payments Operating Lease, Liability Federal Current Federal Tax Expense (Benefit) Common stock—$.01 par value; 60,000,000 shares authorized; 27,888,217 shares issued as of June 30, 2021 and June 30, 2020; 26,549,438 and 26,141,528 shares outstanding as of June 30, 2021 and June 30, 2020 Common Stock, Value, Issued Customer Thirteen Customer Thirteen [Member] Customer Thirteen Weighted average period Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Weighted average grant date fair value per share at June 30, 2020 Weighted average grant date fair value per share at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Customer One [Member] Customer One [Member] Customer one. Operating Leases Lessee, Operating Leases [Text Block] Contract receivable in dispute Contracts Receivable, Claims and Uncertain Amounts Antidilutive Securities Excluded From Computation Of Diluted Earnings Per Share Antidilutive Securities Excluded From Computation Of Diluted Earnings Per Share [Abstract] Antidilutive securities excluded from computation of diluted earnings per share. Disposals Business Combination Disclosure [Text Block] Capacity constraint due to Leverage Ratio Capacity Constraint Due To Senior Leverage Ratio Capacity constraint due to the Senior Leverage Ratio. 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Line of Credit Facility, Maximum Amount Outstanding During Period Line of Credit Facility, Maximum Amount Outstanding During Period Senior Leverage Ratio-Maximum mtrx:SeniorLeverageRatioMaximum Senior Leverage Ratio-Maximum Line of Credit Facility Minimum Unused Capacity Fee-Percentage mtrx:LineofCreditFacilityMaximumUnusedCapacityFeePercentage Line of Credit Facility Maximum Unused Capacity Fee, Percentage Stock compensation expense on nonvested deferred shares Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Stock Options [Member] Share-based Payment Arrangement, Option [Member] Consolidation Items [Domain] Consolidation Items [Domain] Schedule of Acquired Indefinite-lived Intangible Assets by Major Class [Table] Schedule of Acquired Indefinite-lived Intangible Assets by Major Class [Table] Effect of exchange rate changes on cash Effect of Exchange Rate on Cash and Cash Equivalents Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Customer relationship impairment 2 [Member] Customer relationship impairment 2 [Member] Customer relationship impairment 2 Variable Rate [Axis] Variable Rate [Axis] Other income (expense): Other Nonoperating Income (Expense) [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Contributions to other multiemployer plans Multiemployer Plan, Pension, Insignificant, Employer Contribution, Cost Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Prior credit agreement lowest unused credit facility fee Prior credit agreement lowest unused credit facility fee Prior credit agreement lowest unused credit facility fee Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Variable Rate [Domain] Variable Rate [Domain] Additional Paid-In Capital Additional Paid-In Capital [Member] Additional Paid-in Capital [Member] Revenue of Acquiree since Acquisition Date, Actual Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Land and buildings Land Buildings And Improvements Gross Land Buildings And Improvements Gross Customer Seven [Member] Customer Seven [Member] Customer Seven [Member] Employee contribution for next 2% Defined Contribution Plan Employer Matching Contribution Percent For Two percent of Employee Contribution Defined contribution plan employer matching contribution percent for next two percent of employee contribution. Customer relationship impairment 1 [Member] Customer relationship impairment 1 [Member] Customer relationship impairment 1 Other Other Nonoperating Income (Expense) Percentage of employee contribution for next half Percentage of Employee Contribution As Base for Employer Contribution to Match Percentage of employee contribution as base for employer contribution to match Other Lease Information [Abstract] Other Lease Information [Abstract] Other Lease Information Business Combinations [Abstract] Business Combinations [Abstract] Maximum [Member] Maximum [Member] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Share-based Payment Arrangement [Abstract] Carrying value of other intangible assets Intangible Assets, Net (Excluding Goodwill) [Abstract] Award Type [Axis] Award Type [Axis] Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Customer Two [Member] Customer Two [Member] Customer two. Lessee, Operating Lease, Liability, Maturity [Table Text Block] Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of Revenue by Major Customers by Reporting Segments Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block] Aggregate intrinsic value exercisable at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Document Annual Report Document Annual Report CARES Act total benefit CARES Act total benefit CARES Act total benefit Open market purchase of treasury shares Payments for Repurchase of Common Stock Payments for Repurchase of Common Stock Depreciable life of office equipment and software Property, Plant and Equipment, Useful Life Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Prior credit agreement lowest margin Prior Credit Agreement Lowest Margin Prior Credit Agreement Lowest Margin Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Income Tax Authority, Name [Domain] Income Tax Authority, Name [Domain] Ironworkers Mid-America Pension Plan, Local 395 [Member] Ironworkers Mid-America Pension Plan [Member] Ironworkers Mid-America Pension Plan [Member] Operating lease liabilities Non-current operating lease liabilities Operating Lease, Liability, Noncurrent Total Current Income Tax Expense (Benefit) Insurance reserve Deferred Tax Assets Insurance Reserve Deferred tax assets insurance reserve. Gross [Member] Operating Segments [Member] Line Of Credit Basis Spread On CDOR and LIBOR Minimum Line Of Credit Basis Spread On Adjusted LIBO and CDOR Minimum Line of credit basis spread on Adjusted LIBO and CDOR loans rate minimum. Operating lease term (up to) Lessee, Operating Lease, Term of Contract Unused Credit Facility Fee Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Schedule of Recognized Identified Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Charged to Other Accounts SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account Customer Six [Member] Customer Six [Member] Customer Six [Member] Total deferred tax liabilities Deferred Tax Liabilities, Gross Fixed Charge Coverage Ratio, Minimum Fixed Charge Coverage Ratio Minimum Fixed charge coverage ratio minimum. Business Disposals [Line Items] Business Acquisition [Line Items] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Income Statement [Abstract] Income Statement [Abstract] mtrx:StorageAndTerminalSolutions mtrx:StorageAndTerminalSolutions Storage And Terminal Solutions Percentage of limitation on pretax compensation Defined Contribution Plan Maximum Annual Contribution by Employee Percent Maximum percentage of employee gross pay, by the terms of the plan, that the employee may contribute to a defined contribution plan. Significant components of the Company's deferred tax assets and liabilities Components of Deferred Tax Assets and Liabilities [Abstract] Deductions SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Provision (benefit) for federal, state and foreign income taxes Provision (benefit) for federal, state and foreign income taxes Income Tax Expense (Benefit) Accounts receivable, less allowances (2021 - $898; 2020 - $905) Accounts Receivable, after Allowance for Credit Loss, Current Pro-rate of original awards, minimum Payout As Percentage Of Original Award Minimum Payout as percentage of original award minimum. Entity Voluntary Filers Entity Voluntary Filers Total current assets Assets, Current Intellectual Property [Member] Intellectual Property [Member] Total future operating lease payments Lessee, Operating Lease, Liability, to be Paid Shares cancelled Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Change in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Total contributions made Multiemployer Plan, Employer Contribution, Cost Stock-Based Compensation Share-based Payment Arrangement [Policy Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] Property, Plant and Equipment, Type [Domain] Long-Lived Tangible Asset [Domain] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Small Business Entity Small Business CARES ACT deferred payroll tax liability CARES ACT deferred payroll tax liability CARES ACT deferred payroll tax liability Leverage Ratio, Maximum Senior Leverage Ratio Maximum Senior leverage ratio maximum. Grant date fair value Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Equity Component [Domain] Equity Component [Domain] Fiscal 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Deferred tax assets: Components of Deferred Tax Assets [Abstract] Impairment of Intangible Assets, Finite-lived Impairment of Intangible Assets, Finite-lived Warranty reserve working capital provision Warranty reserve working capital provision Amount the Company could have to pay the previous owners, as a working capital adjustment, depending on the amount of unused acquired warranty reserve remaining as of June 30, 2017. Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation, Amount Process and Industrial Facilities Process and Industrial Facilities Segment [Member] Process and Industrial Facilities Segment Adjustment for Final Working Capital Settlement Acquisition Related Adjustment for Final Working Capital Settlement Acquisition related adjustment for the final working capital settlement. Fiscal 2025 Lessee, Operating Lease, Liability, to be Paid, Year Four Time-and-materials Contract Time-and-materials Contract [Member] Income (loss) before income tax expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Research and development and other tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount Segment Reporting [Abstract] Segment Reporting [Abstract] Useful life of intangible assets Finite-Lived Intangible Asset, Useful Life Kvaerner North American Construction [Member] Kvaerner North American Construction [Member] Kvaerner North American Construction [Member] Use of Estimates Use of Estimates, Policy [Policy Text Block] Computation of basic and diluted earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Intangible asset impairments and restructuring costs Restructuring, Settlement and Impairment Provisions Foreign currency translation gain (loss) (net of tax expense (benefit) of $223, $(88) and $27 for the fiscal years ended June 30, 2021, 2020 and 2019, respectively) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Foreign tax credit carryforward [Member] Federal foreign tax credit carryforward [Member] Foreign tax credit carryforward [Member] Common stock, shares authorized Common Stock, Shares Authorized Surcharge Imposed Multiemployer Plan, Pension, Significant, Surcharge [Fixed List] Plumbers and Pipefitters Local Union Seven Four Pension Fund [Member] Plumbers and Pipefitters Local Union Seven Four Pension Fund [Member] Plumbers and Pipefitters Local Union Seven Four Pension Fund [Member] EIN/Pension Plan Number Multiemployer Plans Number Multiemployer plans number. Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Deferred shares vested and released Share Based Compensation Arrangement By Share Based Payment Award Deferred Shares Vested And Released Share based compensation arrangement by share based payment award deferred shares vested and released. Houston Interests, LLC [Member] Houston Interests, LLC [Member] Houston Interests, LLC [Member] Summary of long lived assets according to geographic areas Schedule Of Segment Reporting Information By Geographic Areas [Abstract] Schedule of segment reporting information by geographic areas. Unallocated Corporate [Member] Other Segments [Member] SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] Transportation Equipment [Member] Transportation Equipment [Member] Lease, Cost [Table Text Block] Lease, Cost [Table Text Block] IBEW Local 456 Pension Plan [Member] [Domain] IBEW Local Four Five Six Pension Plan [Member] [Domain] [Domain] for IBEW Local Four Five Six Pension Plan Geographical [Axis] Geographical [Axis] State and Local Jurisdiction [Member] State and Local Jurisdiction [Member] Change in net contract balances Change in net contract balances Change in net contract balances from the prior year to the current year. Foreign tax differential Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Shares available at ESPP Employee Stock Purchase Plan Maximum Number Of Shares Available For Issuance Employee stock purchase plan maximum number of shares available for issuance. Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Other, Description Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Other, Description Storage Solutions [Member] Storage Solutions [Member] Storage solutions. CARES Act interest expense deduction floor CARES Act interest expense deduction floor CARES Act interest expense deduction floor Tax deductible goodwill Business Acquisition, Goodwill, Expected Tax Deductible Amount Net cash used by financing activities Net Cash Provided by (Used in) Financing Activities Less treasury stock, at cost — 1,338,779 and 1,746,689 shares as of June 30, 2021 and June 30, 2020 Treasury Stock, Value Issuance of deferred shares Issuance Of Deferred Shares Issuance of deferred shares. Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Asset Backed Credit Facility LIBOR Rate One Month Add On mtrx:AssetBackedCreditFacilityLIBORRateOneMonthAddOn mtrx:AssetBackedCreditFacilityLIBORRateOneMonthAddOn Restructuring costs Restructuring Charges June 30, 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Three Advances under senior secured revolving credit facility Proceeds from Long-term Lines of Credit Line of Credit Basis Spread on Alternate Base Rate, Maximum mtrx:LineOfCreditBasisSpreadOnAlternateBaseRateMaximum Line of Credit Basis Spread on Alternate Base Rate, Maximum Foreign Tax Authority [Member] Foreign Tax Authority [Member] Excess tax expense (benefit) on stock-based compensation Effect of new accounting standard compared to old standard Effect of new accounting standard compared to old standard Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Fixed Charge Coverage Ratio, Maximum Fixed Charge Coverage Ratio Maximum Fixed charge coverage ratio maximum. Stock Repurchase Program, Number of Shares Authorized to be Repurchased Stock Repurchase Program, Number of Shares Authorized to be Repurchased Restricted Stock or Unit Expense Restricted Stock or Unit Expense Schedule of Quarterly Financial Data (Unaudited) Quarterly Financial Information [Table Text Block] Industrial [Member] Industrial [Member] Industrial. Stock option activity and related information Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Weighted average fair value Share Based Compensation Arrangement By Share Based Payment Award Deferred Shares Vested And Released Weighted Average Grant Date Fair Value Share based compensation arrangement by share based payment award deferred shares vested and released weighted average grant date fair value. State Deferred State and Local Income Tax Expense (Benefit) Non-cash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Significant components of the Company's deferred tax assets and liabilities as reported in the Consolidated Balance Sheets Schedule of Components of Deferred Tax Assets and Liabilities Net [Table Text Block] Schedule of components of deferred tax assets and Liabilities, net. Property, plant and equipment - net Property, Plant and Equipment, Net Amount of non-deductible goodwill impaired. Amount of non-deductible goodwill impaired. Amount of non-deductible goodwill impaired Customer based [Member] Customer Based [Member] Customer based member. Remeasurement of deferred taxes Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Schedule of Finite-Lived Intangible Assets, Future Amortization Expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, Description Multiemployer Plans, Collective-Bargaining Arrangement, Description Total property, plant and equipment - at cost Property, Plant and Equipment, Gross Disclosure Customer Contracts Additional Information [Abstract] Disclosure Customer Contracts Additional Information [Abstract] Disclosure - Customer Contracts - Additional Information [Abstract] Revenue Revenues Company's portion of joint venture equity acquired mtrx_ControllingInterestOfJointVenture,Value mtrx_MatrixShareOfJointVenture,Value Weighted average exercise price at June 30, 2020 Weighted average exercise price at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Tax Credit Carryforward, Description Tax Credit Carryforward, Description Line of Credit Facility Maximum Borrowing Capacity New Agreement-Amount mtrx:MtrxLineOfCreditFacilityMaximumBorrowingCapacityNewAgreementAmount Line of Credit Facility Maximum Borrowing Capacity-New Agreement, Amount Customer Ten Customer Ten [Member] Customer Ten [Member] Document Fiscal Period Focus Document Fiscal Period Focus Employee Stock Purchase Plan, Termination Date Employee Stock Purchase Plan, Termination Date Employee Stock Purchase Plan, Termination Date Federal tax credits Federal tax credit carryforwards [Member] Federal tax credit carryforwards Letters of credit Letters Of Credit Issued Letters of credit issued, excluding insurance-related letters of credit. 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Basic (in shares) Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Basic Diluted earnings (loss) per common share Diluted earnings (loss) per common share (in dollars per share) Earnings Per Share, Diluted Vest in 2019 [Member] Vest in 2018 [Member] Vest in 2018 [Member] Line of credit facility, expiration date Line of Credit Facility, Expiration Date Segment [Domain] Segments [Domain] Repayments of advances under senior secured revolving credit facility Repayments of Long-term Lines of Credit Multiemployer Pension Plans Multiemployer Plan [Table Text Block] Cash paid during the period for income taxes Income Taxes Paid, Net Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Lease, Cost [Abstract] Lease, Cost [Abstract] Other intangible assets Intangible Assets, Net (Excluding Goodwill) Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Fixed-price Contract Fixed-price Contract [Member] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Deferred income taxes Deferred income tax liabilities Deferred Income Tax Liabilities, Net Valuation Allowance Of Deferred Tax Assets - Fully Reserved Tax Credits Valuation Allowance Of Deferred Tax Assets - Fully Reserved Tax Credits Valuation Allowance Of Deferred Tax Assets - Fully Reserved Tax Credits Performance obligations to be recognized as revenue within next twelve months Performance obligations to be recognized as revenue within next twelve months Performance obligations to be recognized as revenue within next twelve months. Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Nonvested Deferred Shares [Member] Nonvested Deferred Shares [Member] Nonvested Deferred Shares [Member] Reconciliation between the expected income tax provision applying the domestic federal statutory tax rate and the reported income tax provision Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Accounts payable Accounts Payable, Current Bad debt reserve Deferred Tax Asset, Tax Deferred Expense, Reserve and Accrual, Accounts Receivable, Allowance for Credit Loss Depreciation and amortization Depreciation and amortization expense Depreciation, Depletion and Amortization Revenue, Major Customer [Line Items] Revenue, Major Customer [Line Items] Accumulated Other Comprehensive Income(Loss) AOCI Attributable to Parent [Member] Inventories Increase (Decrease) in Inventories Restructuring and Related Costs [Table Text Block] Restructuring and Related Costs [Table Text Block] Customer Nine [Member] Customer Nine [Member] Customer Nine [Member] Cost of revenue Cost of Goods and Services Sold Restructuring and Related Activities [Abstract] Proceeds from disposal of business (Note 3) Proceeds from Divestiture of Businesses Proceeds from Divestiture of Businesses Vest in 2021 [Member] Vest in 2021 [Member] Vest in 2021 [Member] CDOR Rate [Member] CDOR Rate [Member] CDOR Rate [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total lease expense Lease, Cost Deferred income tax Deferred Income Tax Expense Benefit Socf Deferred income tax expense benefit socf. Deferred Tax Assets, Tax Deferred Expense Deferred Tax Assets, Tax Deferred Expense Zone Red [Member] Zone Red [Member] Zone red. Property, plant and equipment, at cost: Property, Plant and Equipment, Gross [Abstract] Foreign tax credit carryforwards Foreign tax credit carryforwards [Member] Foreign tax credit carryforwards Asset Backed Credit Facility Fixed Charge Coverage Ratio Requirement Asset Backed Credit Facility Fixed Charge Coverage Ratio Requirement Asset Backed Credit Facility Fixed Charge Coverage Ratio Requirement Open market purchase of treasury shares, shares Treasury Stock, Shares, Acquired Electrical Infrastructure [Member] Electrical Infrastructure [Member] Electrical infrastructure. Treasury shares repurchased to satisfy tax withholding obligations Other Treasury Share Purchases Other treasury share purchases. Receivable holdbacks and other Deferred Tax Liabilities, Other Other assets and liabilities Increase (Decrease) in Other Operating Assets Construction Equipment [Member] Equipment [Member] Line of Credit Facility, Current Borrowing Capacity Line of Credit Facility, Current Borrowing Capacity Number of options vested or expected to vest at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Severance costs and other benefits Severance Costs Revenue, Performance Obligation [Abstract] Revenue, Performance Obligation [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Weighted average remaining contractual life exercisable at June 30, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Earnings Per Share, Basic and Diluted [Abstract] Earnings Per Share, Basic and Diluted [Abstract] Net income (loss) Net income (loss) Net loss Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Schedule of sources of pretax income (loss) Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Gross revenues Gross revenues Gross revenues before intersegment eliminations State tax credit carryforward [Member] State tax credit [Member] Tax credit carryforwards from the state-level taxing authority. Common stock, par value Common Stock, Par or Stated Value Per Share Current assets: Assets, Current [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Finite-Lived Intangible Assets, Gross Gross carrying amount Finite-Lived Intangible Assets, Gross Office equipment and software Office Equipment and Capitalized Computer Software Gross Office equipment and capitalized computer software gross. Entity Central Index Key Entity Central Index Key Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Security Exchange Name Security Exchange Name Exercise of stock options, shares Number of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period OhioCarpentersPensionFundLocal1090and351 OhioCarpentersPensionFundLocal1090and351 [Member] OhioCarpentersPensionFundLocal1090and351 Current Fiscal Year End Date Current Fiscal Year End Date Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Schedule of antidilutive securities excluded from computation of diluted earnings per share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] June 30, 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Five Director Awards [Member] Director Awards [Member] Director Awards [Member] Line Of Credit Basis Spread On Canadian Prime Rate Minimum Line Of Credit Basis Spread On Canadian Prime Rate Minimum Line of credit basis spread on Canadian prime rate minimum. Baillie Tank Equipment, Ltd. [Member] Baillie Tank Equipment, Ltd. [Member] Baillie Tank Equipment, Ltd. [Member] Net cash used by investing activities Net Cash Provided by (Used in) Investing Activities Disaggregation of Revenue [Abstract] Disaggregation of Revenue [Abstract] Changes in operating assets and liabilities increasing (decreasing) cash, net of effects from disposals: Increase (Decrease) in Operating Capital [Abstract] Weighted average grant date fair value per share vested and released Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Increase (Decrease) in Income Taxes Receivable Increase (Decrease) in Income Taxes Receivable Class of Stock [Domain] Class of Stock [Domain] Senior secured revolving credit facility Line of Credit Facility, Maximum Borrowing Capacity Translation adjustment Goodwill, Foreign Currency Translation Gain (Loss) Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Stock Repurchase Program Expiration Date Stock Repurchase Program Expiration Date Northwestern Ohio Plumbers and Pipe Fitters Local 50 [Member] Northwestern Ohio Plumbers and Pipe Fitters Local 50 [Member] Northwestern Ohio Plumbers and Pipe Fitters Local 50 Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Long-Lived Assets Long-Lived Assets Proceeds from issuance of common stock under employee stock purchase plan Proceeds from Stock Plans Other current assets Other Assets, Current Tax over book (book over tax) amortization Deferred Tax Liabilities, Goodwill Expected provision (benefit) for federal income taxes at the statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Type of Deferred Compensation, All Types [Domain] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain] Balance at Beginning of Period Balance at End of Period SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Construction in progress Construction in Progress, Gross Income taxes payable Accrued Income Taxes, Current Utility and Power Infrastructure Member Utility and Power Infrastructure Member [Member] Utility and Power Infrastructure Member Operating Loss Carryforwards, Limitations on Use Operating Loss Carryforwards, Limitations on Use Inventories Inventory, Policy [Policy Text Block] Foreign Current Foreign Tax Expense (Benefit) Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities, net of effects of disposals: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]