Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] 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] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Business Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Carrying Value of Goodwill by Segment Schedule of Goodwill [Table Text Block] Carrying Value of Other Intangible Assets Schedule Of Intangible Assets Excluding Goodwill Table [Text Block] Schedule of intangible assets excluding goodwill. Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Lessee, Operating Lease, Liability, Payment, Due [Abstract] Remainder of Fiscal 2020 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year Fiscal 2021 Lessee, Operating Lease, Liability, Payments, Due Year Two Fiscal 2022 Lessee, Operating Lease, Liability, Payments, Due Year Three Fiscal 2023 Finance Lease, Liability, Payments, Due Year Four Fiscal 2024 Finance Lease, Liability, Payments, Due Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five Total future operating lease payments Lessee, Operating Lease, Liability, Payments, Due Less: imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Net present value of future lease payments Operating Lease, Liability Less: current portion of operating lease liabilities Operating Lease, Liability, Current Non-current operating lease liabilities Operating Lease, Liability, Noncurrent Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract Total future payments for lease not yet commenced Total future payments for lease not yet commenced Total future payments for lease not yet commenced Cover page. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Address, Address Line One Entity Address, Address Line One Entity File Number Entity File Number Security Exchange Name Security Exchange Name Title of 12(b) Security Title of 12(b) Security Document Transition Report Document Transition Report Document Quarterly Report Document Quarterly Report 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 Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Shell Company Entity Shell Company Entity Tax Identification Number Entity Tax Identification Number Leases [Abstract] Lease, Cost [Table Text Block] Lease, Cost [Table Text Block] Lessee, Operating Lease, Liability, Maturity [Table Text Block] Lessee, Operating Lease, Liability, Maturity [Table Text Block] Other Information Related to Leases [Table Text Block] Other Information Related to Leases [Table Text Block] Table disclosing operating lease weighted average remaining lease term, weighted average discount rate, and supplemental cash flow disclosures. Statement of Cash Flows [Abstract] Operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net income to net cash provided by operating activities, net of effects from acquisitions and disposals: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Deferred income tax Deferred Income Tax Expense (Benefit) Gain on disposal of business Gain (Loss) on Disposition of Business Gain on sale of property, plant and equipment Gain (Loss) on Disposition of Property Plant Equipment Provision for uncollectible accounts Accounts Receivable, Credit Loss Expense (Reversal) Other Other Noncash Income (Expense) Changes in operating assets and liabilities increasing (decreasing) cash, net of effects from acquisitions and disposals: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Costs and estimated earnings in excess of billings on uncompleted contracts Increase (Decrease) in Cost in Excess of Billing on Uncompleted Contract Inventories Increase (Decrease) in Inventories Other assets and liabilities Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Billings on uncompleted contracts in excess of costs and estimated earnings Increase (Decrease) in Billing in Excess of Cost of Earnings Accrued expenses Increase (Decrease) in Accrued Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures Payments to Acquire Property, Plant, and Equipment Acquisition, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from disposal of business Proceeds from Divestiture of Businesses Proceeds from asset sales Proceeds from Sale of Productive Assets Net cash provided (used) by investing activities Net Cash Provided by (Used in) Investing Activities Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Advances under senior secured revolving credit facility Proceeds from Long-term Lines of Credit Repayments of advances under senior secured revolving credit facility Repayments of Long-term Lines of Credit Payments of debt issuance costs Payments of Debt Issuance Costs Open market purchase of treasury shares Payments for Repurchase of Common Stock Issuances of common stock Proceeds from Issuance of Common Stock Proceeds from issuance of common stock under employee stock purchase plan Proceeds from Stock Plans Repurchase of common stock for payment of statutory taxes due on equity-based compensation Payments for Repurchase of Other Equity Capital contributions from noncontrolling interest Proceeds from Noncontrolling Interests Excess tax benefit of exercised stock options and vesting of deferred shares Excess Tax Benefit from Share-based Compensation, Financing Activities Repayments of acquired long-term debt Repayments of Long-term Debt Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents Increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents, end of period Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Income taxes Income Taxes Paid, Net Interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Non-cash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Purchases of property, plant and equipment on account Capital Expenditures Incurred but Not yet Paid Accrual for unsettled stock repurchases Accrual for unsettled stock repurchases Accrual for unsettled stock repurchases Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Presentation Basis of Presentation and Significant Accounting Policies [Text Block] Impairment charge Goodwill, Impairment Loss Amortization expense Amortization of Intangible Assets Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Baillie Tank Equipment, Ltd. [Member] Baillie Tank Equipment, Ltd. [Member] Baillie Tank Equipment, Ltd. [Member] Houston Interests, LLC [Member] Houston Interests, LLC [Member] Houston Interests, LLC [Member] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Intellectual Property [Member] Intellectual Property [Member] Customer Relationships [Member] Customer Relationships [Member] Noncompete Agreements [Member] Noncompete Agreements [Member] Trade Names [Member] Trade Names [Member] Other Intangible Assets [Member] Other Intangible Assets [Member] SM Electric Trade Name [Member] SM Electric Trade Name [Member] SM Electric Trade Name [Member] Acquired Finite-lived Intangible Asset, Residual Value Acquired Finite-lived Intangible Asset, Residual Value Finite-Lived Intangible Assets, Gross Finite-Lived Intangible Assets, Gross Finite-Lived Intangible Asset, Useful Life Finite-Lived Intangible Asset, Useful Life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Finite-lived Intangible Assets, Fair Value Disclosure Finite-lived Intangible Assets, Fair Value Disclosure Backlog received in exchange for settled account receivable Backlog received in exchange for settled account receivable Backlog received in exchange for settled account receivable, amount of backlog to be recognized as revenue in the future. Indefinite-Lived Trade Names Finite-Lived Trade Names, Gross 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] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock Options [Member] Share-based Payment Arrangement, Option [Member] Nonvested Deferred Shares [Member] Nonvested Deferred Shares [Member] Nonvested Deferred Shares [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total antidilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Statement of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Accounts receivable, less allowances (September 30, 2019— $1,091 and June 30, 2019—$923) Accounts Receivable, after Allowance for Credit Loss, Current Costs and estimated earnings in excess of billings on uncompleted contracts Contract with Customer, Asset, before Allowance for Credit Loss Deferred income taxes Deferred Tax Assets, Net of Valuation Allowance, Current Inventories Inventory, Net Income taxes receivable Income Taxes Receivable, Current Other current assets Other Assets, Current Total current assets Assets, Current Property, plant and equipment at cost: Property, Plant and Equipment, Gross [Abstract] Land and buildings Buildings and Improvements, Gross Construction equipment Machinery and Equipment, Gross Transportation equipment Transportation Equipment Gross Transportation Equipment Gross Office equipment and software Furniture and Fixtures, Gross Construction in progress Construction in Progress, Gross Property, plant and equipment at cost, gross Property, Plant and Equipment, Gross Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant and equipment at cost, net Property, Plant and Equipment, Net Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Goodwill Goodwill Other intangible assets Intangible Assets, Net (Excluding Goodwill) Deferred income taxes Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Other assets Other Assets, Noncurrent Total assets Assets Liabilities and stockholders’ equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Billings on uncompleted contracts in excess of costs and estimated earnings Billings in Excess of Cost Accrued wages and benefits Employee-related Liabilities, Current Accrued insurance Accrued Insurance, Current Operating lease liabilities Income taxes payable Accrued Income Taxes, Current Deferred Tax Liabilities, Net, Current Deferred Tax Liabilities, Net, Current Other accrued expenses Other Liabilities, Current Total current liabilities Liabilities, Current Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Operating lease liabilities Borrowings under senior secured revolving credit facility Long-term Debt, Excluding Current Maturities Other liabilities Liabilities, Other than Long-term Debt, Noncurrent Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Matrix Service Company stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock—$.01 par value; 60,000,000 shares authorized; 27,888,217 shares issued as of September 30, 2019 and June 30, 2019; 27,131,446 and 26,807,203 shares outstanding as of September 30, 2019 and June 30, 2019 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Matrix Service Company stockholders' equity Stockholders' Equity before Treasury Stock Less: Treasury stock, at cost — 756,771 shares as of September 30, 2019, and 1,081,014 shares as of June 30, 2019 Treasury Stock, Value Total stockholders' equity Stockholders' Equity Attributable to Parent Noncontrolling interest Stockholders' Equity Attributable to Noncontrolling Interest Total liabilities and stockholders’ equity Liabilities and Equity Schedule of Goodwill [Table] Schedule of Goodwill [Table] Electrical Infrastructure [Member] Electrical Infrastructure [Member] Electrical infrastructure. Oil Gas & Chemical [Member] Oil Gas And Chemical [Member] Oil gas & chemical. Storage Solutions [Member] Storage Solutions [Member] Storage solutions. Industrial [Member] Industrial [Member] Industrial. Reporting Unit [Member] Reporting Unit [Member] Reporting unit at risk for impairment Other Segments [Member] Other Segments [Member] Goodwill [Line Items] Goodwill [Line Items] Goodwill Goodwill, Gross Cumulative impairment loss Goodwill, Impaired, Accumulated Impairment Loss Goodwill Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount Goodwill [Roll Forward] Goodwill [Roll Forward] Net balance at June 30, 2019 Goodwill, Acquired During Period Goodwill, Acquired During Period Goodwill, Written off Related to Sale of Business Unit Goodwill, Written off Related to Sale of Business Unit Goodwill, Purchase Accounting Adjustments Goodwill, Purchase Accounting Adjustments Translation adjustment Goodwill, Foreign Currency Translation Gain (Loss) Net balance at September 30, 2019 Leases Lessee, Leases [Policy Text Block] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Text Block] Revenue from Contract with Customer [Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Treasury Stock Treasury Stock [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Noncontrolling Interest Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Beginning equity balances, as adjusted Beginning equity balances, as adjusted Beginning equity balances as adjusted for the effects of retrospective impacts of the adoption of a new accounting standard. Retrospective adjustment upon adoption of ASU 2016-09 Cumulative Effect of New Accounting Principle in Period of Adoption Noncontrolling Interest, Increase from Subsidiary Equity Issuance Noncontrolling Interest, Increase from Subsidiary Equity Issuance Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Open market purchases of treasury shares Treasury Stock, Value, Acquired, Cost Method Treasury shares sold to Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Issuance of deferred shares Adjustments to Additional Paid in Capital, Other Other Treasury Share Purchases Other Treasury Share Purchases Other treasury share purchases. Payments to Acquire Interest in Joint Venture Payments to Acquire Interest in Joint Venture Noncontrolling interest of consolidated joint venture Noncontrolling Interest, Increase from Business Combination Open market purchases of treasury shares (310,532 shares) Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Stock-based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Cash paid for operating leases Operating Lease, Payments Right-of-use asset obtained in exchange for operating lease liability Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Revenue, Performance Obligation [Abstract] Revenue, Performance Obligation [Abstract] Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation, Amount 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. Contract with Customer, Asset and Liability [Abstract] Contract with Customer, Asset and Liability [Abstract] Costs and estimated earnings in excess of billings on uncompleted contracts Change in CIE Change in CIE Change in CIE from prior year to the current period. Billings on uncompleted contracts in excess of costs and estimated earnings Contract with Customer, Liability, Current Change in BIE Change in BIE Change in BIE from the prior year to the current period. Change in net contract balances Change in net contract balances Change in net contract balances from the prior year to the current year. Contract with Customer, Liability, Revenue Recognized Contract with Customer, Liability, Revenue Recognized Disclosure Customer Contracts Additional Information [Abstract] Disclosure - Customer Contracts - Additional Information [Abstract] Costs incurred and estimated earnings recognized on uncompleted contracts Uncompleted Contracts Costs Incurred And Estimated Earnings Recognized Uncompleted contracts costs incurred and estimated earnings recognized. Billings on uncompleted contracts Uncompleted Contracts Billings Uncompleted contracts billings. Total Uncompleted Contracts Net Uncompleted contracts. Contract Receivable Retainage, Due in Next Twelve Months Contract Receivable Retainage, Next Twelve Months Contract Receivable Retainage, Due after Next Twelve Months Contract Receivable Retainage, after Next Twelve Months Disaggregation of Revenue [Abstract] Disaggregation of Revenue [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES Canada CANADA Other international [Member] Other international [Member] Other international [Member] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Fixed-price Contract [Member] Fixed-price Contract [Member] Time-and-materials Contract [Member] Time-and-materials Contract [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue from Contract with Customer, Including Assessed Tax Revenue from Contract with Customer, Including Assessed Tax Statement Condensed Consolidated Balance Sheets [Abstract] Statement Condensed Consolidated Balance Sheets [Abstract] Accounts receivable, allowances Accounts Receivable, Allowance for Credit Loss, Current 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 Common stock, shares outstanding Shares, Outstanding Treasury stock, shares Treasury Stock, Shares Statement of Comprehensive Income [Abstract] Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Other Lease Information [Abstract] Other Lease Information [Abstract] Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Discount Rate, Percent Operating Lease, Weighted Average Discount Rate, Percent Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Income Statement [Abstract] Revenues Revenues Cost of revenues Cost of Goods and Services Sold Gross profit Gross Profit Selling, general and administrative expenses Selling, General and Administrative Expense Operating income Operating Income (Loss) Other income (expense): Other Nonoperating Income (Expense) [Abstract] Interest expense Interest Expense Interest income Investment Income, Interest Other Other Nonoperating Income (Expense) Income before income tax expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Provision for federal, state and foreign income taxes Income Tax Expense (Benefit) Net income Less: Net income attributable to noncontrolling interest Net Income (Loss) Attributable to Noncontrolling Interest Basic earnings per common share (US$ per share) Earnings Per Share, Basic Diluted earnings per common share (US$ per share) Earnings Per Share, Diluted Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (shares) Weighted Average Number of Shares Outstanding, Basic Diluted (shares) Weighted Average Number of Shares Outstanding, Diluted Segment Reporting [Abstract] Results of Operations Schedule of Segment Reporting Information, by Segment [Table Text Block] Earnings per Common Share Earnings Per Share [Text Block] Commitments and Contingencies Disclosure [Abstract] Project Unapproved Change Orders and Claims [Table] Power Generation Project Unapproved Change Orders and Claims [Table] Power Generation Project Unapproved Change Orders and Claims [Table] Project [Axis] Power Generation Project [Axis] Power Generation Project [Axis] Power Generation Project [Domain] Power Generation Project [Domain] [Domain] for Power Generation Project [Axis] Unapproved Change Orders On Power Generation Project [Member] Unapproved Change Orders On Power Generation Project [Member] Unapproved Change Orders On Power Generation Project [Member] Claim On Power Generation Project [Member] Claim On Power Generation Project [Member] Claim On Power Generation Project [Member] Project Unapproved Change Orders and Claims [Line Items] Power Generation Project Unapproved Change Orders and Claims [Line Items] [Line Items] for Power Generation Project Unapproved Change Orders and Claims [Table] Unapproved change orders and claims Contract Cost, Unapproved Change Order, Amount Lessee, Operating Leases [Text Block] Lessee, Operating Leases [Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Kvaerner NAC Kvaerner North American Construction [Member] Kvaerner North American Construction [Member] Intersegment Eliminations [Member] Intersegment Eliminations [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Gross revenues Gross revenues Gross revenues before intersegment eliminations Gross profit Operating income Segment assets Schedule of Acquired Indefinite-lived Intangible Assets by Major Class [Table] Schedule of Acquired Indefinite-lived Intangible Assets by Major Class [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] CDOR Rate [Member] CDOR Rate [Member] CDOR Rate [Member] Canadian Prime Rate [Member] Canadian Prime Rate [Member] Canadian Prime Rate [Member] Debt Amendment [Member] Debt Amendment [Member] August 31, 2017 Debt Amendment Terms Credit Agreement Terms Acquired Indefinite-lived Intangible Assets [Line Items] Credit Agreement Term Credit Agreement Term Credit Agreement Term Senior secured revolving credit facility Line of Credit Facility, Maximum Borrowing Capacity Line Of Credit Facility Expiration Date mtrx_LineOfCreditFacilityExpirationDate Credit Facility Expiration Date Senior Leverage Ratio, Acquisition Period, Maximum Senior Leverage Ratio, Acquisition Period, Maximum Senior Leverage Ratio, Acquisition Period, Maximum Senior Leverage Ratio, Acquisition Period, Minimum Senior Leverage Ratio, Acquisition Period, Minimum Senior Leverage Ratio, Acquisition Period, Minimum Senior Leverage Ratio, Maximum Senior Leverage Ratio Max Senior Leverage Ratio Max Senior Leverage Ratio, Minimum Senior Leverage Ratio Min Senior Leverage Ratio Minimum Fixed Charge Coverage Ratio, Maximum Fixed Charge Coverage Ratio Maximum Fixed charge coverage ratio maximum. Fixed Charge Coverage Ratio, Minimum Fixed Charge Coverage Ratio Minimum Fixed charge coverage ratio minimum. Amount of Limit on Asset Dispositions Amount Of Limit On Asset Dispositions Amount of limit on asset dispositions. Additional Margin on alternate base rate loans, Minimum Line Of Credit Basis Spread On Alternate Base Rate Minimum Line of credit basis spread on alternate base rate minimum. 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. Additional Margin on LIBOR loans, Minimum Line Of Credit Basis Spread On London Interbank Offered Rate Minimum Line of credit basis spread on London interbank offered rate minimum. Additional Margin on LIBOR loans, Maximum Line Of Credit Basis Spread On London Interbank Offered Rate Maximum Line of credit basis spread on London interbank offered rate maximum. Sublimit on Australian Dollar, Canadian Dollar, Euro and Pounds Sterling Sublimit on Australian Dollar, Canadian Dollar, Euro and Pounds Sterling Sublimit on Australian Dollar, Canadian Dollar, Euro and Pounds Sterling Sub-limit on letters of credit under the credit facility Sub-limit on letters of credit under the credit facility Sub-limit on letters of credit under the credit facility. Additional Margin on Adjusted LIBO, EURIBO and CDOR loans, Minimum Line Of Credit Basis Spread On Adjusted LIBO, EURIBO and CDOR Minimum Line of credit basis spread on Adjusted LIBO, EURIBO and CDOR loans rate minimum. Additional Margin on Adjusted LIBO, EURIBO and CDOR loans, Maximum Line Of Credit Basis Spread On Adjusted LIBO, EURIBO and CDOR Maximum Line of credit basis spread on Adjusted LIBO, EURIBO and CDOR loans rate maximum. Additional Margin on Canadian prime rate loans, Minimum Line Of Credit Basis Spread On Canadian Prime Rate Minimum Line of credit basis spread on Canadian prime rate minimum. Additional Margin on Canadian prime rate loans, Maximum Line Of Credit Basis Spread On Canadian Prime Rate Maximum Line of credit basis spread on Canadian prime rate maximum. CDOR Rate description Line Of Credit Facility Canadian Deposit Offered Rate Description Line of credit facility Canadian deposit offered rate description. Variable rate basis Debt Instrument, Description of Variable Rate Basis Basis spread on variable rate basis Debt Instrument, Basis Spread on Variable Rate Canadian prime rate description Line Of Credit Facility Canadian Prime Rate Description Line of credit facility Canadian prime rate description. Unused Credit Facility Fee Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Maximum limit of consolidated funded indebtedness Maximum Limit Of Consolidated Funded Indebtedness Maximum limit of consolidated funded indebtedness. Consolidated EBITDA as defined in the Credit Agreement Consolidated Earnings Before Interest Taxes Depreciation And Amortization Per Credit Agreement Consolidated earnings before interest taxes depreciation and amortization per credit. Consolidated funded indebtedness Consolidated Funded Indebtedness Consolidated Funded Indebtedness Minimum Consolidated EBITDA Required Minimum Consolidated EBITDA Required Minimum Consolidated EBITDA required under the August 31, 2017 credit amendment. Restricted Payments Under Credit Amendment Restricted Payments Under Credit Amendment Payment of dividends and share repurchases the August 31, 2017 credit amendment is restricted to an aggregate of $5.0 million. Leverage Ratio Allowed for Restricted Payments, Maximum Leverage Ratio Allowed for Restricted Payments, Maximum Leverage Ratio Allowed for Restricted Payments, Maximum Leverage Ratio Allowed for Restricted Payments, Minimum Leverage Ratio Allowed for Restricted Payments, Minimum Leverage Ratio Allowed for Restricted Payments, Minimum Dividend Restriction Under Credit Agreement, Percent Dividend Restriction Under Credit Agreement Dividend Restriction Under Credit Agreement, as a percentage of net income for the the fiscal year. Dividend Restriction Under Credit Agreement, Amount Dividend Restriction Under Credit Agreement, Amount Dividend restriction under credit agreement, amount in dollars. Expected Remaining Amortization Expense [Abstract] Expected Remaining Amortization Expense [Abstract] Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Finite-Lived Intangible Assets, Amortization Expense, Next Year Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Finite-Lived Intangible Assets, Amortization Expense, Year Two Finite-Lived Intangible Assets, Amortization Expense, Year Two Finite-Lived Intangible Assets, Amortization Expense, Year Three Finite-Lived Intangible Assets, Amortization Expense, Year Three Finite-Lived Intangible Assets, Amortization Expense, Year Four Finite-Lived Intangible Assets, Amortization Expense, Year Four Finite-Lived Intangible Assets, Amortization Expense, Year Five Finite-Lived Intangible Assets, Amortization Expense, Year Five Finite-Lived Intangible Assets, Amortization Expense, after Year Five Finite-Lived Intangible Assets, Amortization Expense, after Year Five Finite-Lived Intangible Assets, Net Finite-Lived Intangible Assets, Net Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign currency translation gain (loss) (net of tax expense (benefit) of ($22) and $62 for the three months ended September 30, 2019 and 2018, respectively) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: Comprehensive income attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to Matrix Service Company Comprehensive Income (Loss), Net of Tax, Attributable to Parent Availability Under the Senior Credit Facility Schedule of Line of Credit Facilities [Table Text Block] Computation of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Antidilutive Securities Excluded from the Calculation of Diluted EPS Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Operating Lease, Liability Intangible Assets Including Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Contract with Customer, Asset and Liability [Table Text Block] Contract with Customer, Asset and Liability [Table Text Block] Disaggregation of Revenue [Table Text Block] Disaggregation of Revenue [Table Text Block] Segment Information Segment Reporting Disclosure [Text Block] Treasury Stock, Shares, Acquired Treasury Stock, Shares, Acquired Employee Stock Purchase Plan, shares Stock Issued During Period, Shares, Employee Stock Purchase Plans Exercise of stock options, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of deferred shares, shares Deferred Shares Issued Deferred Shares Issued Other treasury shares purchases, shares Other Treasury Shares Acquired Other treasury shares acquired. Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Operating lease term (up to) Lessee, Operating Lease, Term of Contract Percentage of real estate leases Percentage of real estate leases Percentage of leases - real estate Senior credit facility Capacity Constraint Due To Senior Leverage Ratio Capacity Constraint Due To Senior Leverage Ratio Capacity constraint due to the Senior Leverage Ratio. Line Of Credit Facility Maximum Borrowing Capacity After Consideration Of Capacity Constraint Line Of Credit Facility Maximum Borrowing Capacity After Consideration Of Capacity Constraint Line of credit facility maximum borrowing capacity after consideration of capacity constraint. Line of Credit Facility, Amount Outstanding Long-term Line of Credit Letters of credit subject to the credit facility Letters Of Credit Subject To Credit Facility Letters Of Credit Subject To Credit Facility. Availability under the senior credit facility Line of Credit Facility, Remaining Borrowing Capacity Prior federal income tax rate Prior federal income tax rate Federal income tax rate prior to the Tax Cuts and Jobs Act. Blended income tax rate Blended income tax rate Blended income tax rate of 28.06% used by the Company for the remainder of Fiscal 2018. The use of this blended rate is stipulated by the Internal Revenue Code in connection with the Tax Cuts and Jobs Act of December 2017, which reduced the federal income tax rate from 35% to 21%. Since the Company has a June 30 fiscal year end, it must use a blend of 21% and 35% for the rest of the current fiscal year. Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Restriction of deductibility of certain executive compensation Restriction of deductibility of certain executive compensation Restriction of deductibility of certain executive compensation in excess of $1.0 million. Description of one of the major changes in connection with the Tax Cuts and Jobs Act of December 2017. Deferred Tax Assets, Net Deferred Tax Assets, Net Effective Income Tax Rate Reconciliation, Percent Effective Income Tax Rate Reconciliation, Percent Deferred tax remeasurement Deferred tax remeasurement Deferred tax remeasurement due to the enactment of the Tax Cuts and Jobs Act of 2017. The Company's domestic net deferred tax liability balance was remeasured at a lower corporate tax rate, which reduced the net deferred tax liability balance. The downward remeasurement was recorded as a benefit to income tax expense. Deferred Tax Assets, Tax Credit Carryforwards, Foreign Deferred Tax Assets, Tax Credit Carryforwards, Foreign Tax Credit Carryforward, Valuation Allowance Tax Credit Carryforward, Valuation Allowance Deferred Tax Assets, Foreign Tax Credit Carryforward, After Valuation Allowance Deferred Tax Assets, Foreign Tax Credit Carryforward, After Valuation Allowance Deferred Tax Assets, Foreign Tax Credit Carryforward, After Valuation Allowance Amount of Foreign Tax Credit Carryforward Expiring in Fiscal 2021 Amount of Foreign Tax Credit Carryforward Expiring in Fiscal 2021 Amount of Foreign Tax Credit Carryforward Expiring in Fiscal 2021 Amount of Foreign Tax Credit Carryforward Expiring Between Fiscal 2023 and Fiscal 2025 Amount of Foreign Tax Credit Carryforward Expiring in Fiscal 2023 Amount of Foreign Tax Credit Carryforward Expiring in Fiscal 2023 Discrete item impact on effective tax rate Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Deferred Tax Liabilities, Net Deferred Tax Liabilities, Net Expected effective tax rate Expected effective tax rate Expected effective tax rate next fiscal year. Lease, Cost [Abstract] Operating lease expense Operating Lease, Cost Short-term lease expense Short-term Lease, Cost Total lease expense Lease, Cost Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Carrying Amount Indefinite Trade Names Indefinite-Lived Trade Names Total intangible assets, net carrying amount Earnings Per Share, Basic [Abstract] Earnings Per Share, Basic [Abstract] Net income (loss) Net Income (Loss) Attributable to Parent Weighted average shares outstanding - basic (shares) Basic EPS (US$ per share) Earnings Per Share, Diluted [Abstract] Earnings Per Share, Diluted [Abstract] Dilutive stock options Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Dilutive nonvested deferred shares Incremental Common Shares Attributable to Dilutive Effect of Nonvested Shares with Forfeitable Dividends Diluted weighted average shares (shares) Diluted EPS (US$ per share)