75000 - Document - Document and Entity Information link:presentationLink link:calculationLink link:definitionLink 75010 - Statement - Statements of Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75020 - Statement - Statement of Changes in Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75030 - Disclosure - Description of The Plan link:presentationLink link:calculationLink link:definitionLink 75040 - Disclosure - Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 75050 - Disclosure - Concentration of Risk link:presentationLink link:calculationLink link:definitionLink 75060 - Disclosure - Fair Value Measurement link:presentationLink link:calculationLink link:definitionLink 75070 - Disclosure - Tax Status link:presentationLink link:calculationLink link:definitionLink 75080 - Disclosure - Related Party and Party-in-interest Transactions link:presentationLink link:calculationLink link:definitionLink 75090 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 75100 - Disclosure - Schedule of Assets (Held at End of Year) link:presentationLink link:calculationLink link:definitionLink 75110 - Disclosure - Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 75120 - Disclosure - Description of The Plan (Tables) link:presentationLink link:calculationLink link:definitionLink 75130 - Disclosure - Concentration of Risk (Tables) link:presentationLink link:calculationLink link:definitionLink 75140 - Disclosure - Fair Value Measurement (Tables) link:presentationLink link:calculationLink link:definitionLink 75150 - Disclosure - Schedule of Assets (Held at End of Year) (Tables) link:presentationLink link:calculationLink link:definitionLink 75160 - Disclosure - Description of The Plan - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75170 - Disclosure - Description of The Plan - Summary of Six Year Graded Vesting Schedule (Details) link:presentationLink link:calculationLink link:definitionLink 75180 - Disclosure - Summary Of Significant Accounting Policies (Additional Information) (Details) link:presentationLink link:calculationLink link:definitionLink 75190 - Disclosure - Concentration of Risk - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75200 - Disclosure - Concentration of Risk - Summary of Fair Value of Individual Investments Represents 10% or More of Plan's Net Assets Available for Benefits (Details) link:presentationLink link:calculationLink link:definitionLink 75210 - Disclosure - Fair Value Measurement - Summary of Fair Value Hierarchy of Plan's Assets (Details) link:presentationLink link:calculationLink link:definitionLink 75220 - Disclosure - Fair Value Measurement - Summary of Fair Value of Investments Measured at Net Asset Value as Practical Expedient (Details) link:presentationLink link:calculationLink link:definitionLink 75230 - Disclosure - Tax Status - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75240 - Disclosure - Related Party and Party-in-interest Transactions - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75250 - Disclosure - Subsequent Events - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75260 - Disclosure - Schedule of Assets (Held at End of Year) (Details) link:presentationLink link:calculationLink link:definitionLink 75260 - Disclosure - Schedule of Assets (Held at End of Year) (Details) [Default] link:presentationLink link:calculationLink link:definitionLink EBP Note Receivable From Participant Borrowing Term EBPNote receivable from participant borrowing term. Note receivable from participant borrowing term EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Additions to Net Assets Employee Benefit Plan, Minimum Number of Hours to be Completed to be Entitled to Safe Harbor Matching Contribution Employee benefit plan, minimum number of hours to be completed to be entitled to Safe Harbor matching contribution. Minimum hours to be completed, to be entitled to Safe Harbor matching contribution EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid to participants MGRC Unitized Stock Fund MGRC Unitized Stock Fund [Member] MGRC Unitized Stock Fund member. Employee Benefit Plan Company Matching Contributions Vesting Percentage Employee benefit plan company matching contributions vesting percentage. Vesting Percentage EBP, Receivable [Abstract] Receivables: Fair Value, Inputs, Level 2 [Member] Level 2 EBP, Related Party and Party-in-Interest Transactions [Line Items] Document Fiscal Period Focus Employer contributions EBP, Employer Contribution, Receivable EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Forfeitures of common stock and cash EBP, Tax Status [Abstract] EBP, Forfeited Nonvested Account Balance of unallocated forfeitures EBP, Description of Plan [Text Block] Description of The Plan EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Interest income on participants loans Investment, Identifier [Axis] EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Administrative fees EBP, Description of Plan [Line Items] EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Investment, Fair Value and NAV [Abstract] Five Year But Less Than Six Years [Member] Five year but less than six years. 5 Years but less than 6 Years Years of Service [Domain] Years of service domain. EBP, Liability [Abstract] Liabilities EBP, Accounting Policy [Line Items] EBP, Schedule of Asset Held for Investment [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] T Rowe Price Target Date Retirement Funds [Member] T rowe price target date retirement funds. T Row Price Target-date Retirement Funds EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Note receivable from participant account maximum borrowing Common Collective Trust [Member] Collective investment trusts at NAV Amendment Flag EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash, Total Employer contributions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Deductions from Net Assets EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Note receivable from participant account minimum borrowing Payment of Benefits EBP, Payment to Participant [Policy Text Block] Concentration of investment benchmark threshold percentage EBP, Risk and Uncertainty, Concentration of Investment, Benchmark Threshold Percentage EBP, Risk and Uncertainty, Concentration of Investment at Fair Value to Net Assets, Amount McGrath RentCorp Unitized Stock Fund EBP, Schedule of Asset Held for Investment [Line Items] Fair Value Hierarchy and NAV [Axis] EBP, Employer, Common Stock Fund [Member] McGrath RentCorp Common Stock EBP, Investment, Current Value, Type [Extensible Enumeration] Investment Type [Axis] Years of Service [Axis] Years of service. Three Year But Less Than Four Years [Member] Three year but less than four years. 3 Years but less than 4 Years Document Type Entity Central Index Key EBP, Self-Directed Brokerage Account [Member] Brokerage accounts EBP, Forfeited Nonvested Account, Decrease from Administrative Expense Investment and administrative costs EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition 4 Years but less than 5 Years Four Year But Less Than Five Years [Member] Four year but less than five years. EBP, Contribution, Participating Employer [Axis] EBP, Subsequent Event [Table] EBP, Accounting Policy [Table] EBP, Subsequent Event [Abstract] EBP, Basis of Accounting [Policy Text Block] Basis of Accounting EBP, Description of Plan [Table] Harbor Capital Appreciation [Member] Harbor capital appreciation. Harbor Capital Appreciation Employee Benefit Plan, Participant Vested Percentage Employee benefit plan, participant vested percentage. Participant percentage vested EBP, Employer, Common Stock [Member] Common Stock EBP, Investment, Fair Value [Abstract] Investments: Northern Trust [Member] Northern Trust. Northern Trust EBP, Investment, Number of Shares Number of shares Minimum [Member] Minimum EBP, Related Party and Party-in-Interest Transactions [Text Block] Related Party and Party-in-interest Transactions Total additions to net assets EBP, Change in Net Asset Available for Benefit, Increase Fair Value, Inputs, Level 3 [Member] Level 3 Less Than Two Years [Member] Less than two years. Less than 2 Years EBP, Change in Net Asset Available for Benefit, Increase from Contribution Total contributions Asset Excluding Collective Investment Trusts [Member] Asset excluding collective investment trusts. Total assets held in fair value hierarchy EBP, Expense [Policy Text Block] Administrative Expenses Employee Benefit Plan Participant Loan Term Employee benefit plan participant loan term. Term EBP, Other Liability Other liabilities EBP, Accrued Expense Accrued expenses Fair Value Measured at Net Asset Value Per Share [Member] Fair Value Measured at Net Asset Value Per Share EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Participants deferral contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Contributions: EBP, Tax Determination Letter, Date Tax determination letter, date EBP, Liability Total liabilities EBP, Participant Contribution, Automatic, Deferral Rate Percentage of employee's deferral EBP, Contribution, Participating Employer [Domain] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value, Ending Balance EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value, Beginning Balance Total Investments Total Fair value Total investments at fair value EBP, Use of Estimate [Policy Text Block] Use of Estimates Mutual Fund [Member] Mutual funds Entity [Domain] EBP, Summary of Accounting Policy [Text Block] Summary of Significant Accounting Policies Fair Value Measurement EBP, Investment, Fair Value and NAV [Text Block] EBP, Description of Plan and Accounting Change [Abstract] EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Notes Receivable from Participants EBP, Statement of Change in Net Asset Available for Benefit [Line Items] Redemption frequency (if currently eligible) Employee Benefit Plan Fair Value Investment Net Asset Value Redemption Frequency Employee benefit plan fair value investment net asset value redemption frequency. Statistical Measurement [Domain] EBP, Note Receivable from Participant Notes receivable from participants Document Period End Date EBP, Risk and Uncertainty [Table] Fair Value Hierarchy and NAV [Domain] EBP, Risk and Uncertainty [Policy Text Block] Risks and Uncertainties EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Note receivable from participant account maximum borrowing percentage EBP, Tax Determination Letter, Obtained [true false] Tax determination letter, obtained EBP, Related Party and Party-in-Interest Transactions [Table] EBP Note Receivable From Participant Principal Residence Maximum Borrowing Term EBP note receivable from participant principal residence maximum borrowing term. Note receivable from participant principal residence maximum borrowing term EBP, Subsequent Event [Text Block] Subsequent Events Employee Benefit Plan Lump Sum Payable Margin On Termination Employee benefit plan lump sum payable margin on termination. Lump sum payable margin on termination EBP, Subsequent Event, Description Subsequent event, description EBP, Participant Contribution, Pretax, Maximum Annual Compensation, Amount Compensation Cover [Abstract] Employee Benefit Plan Schedule Of Assets Held At End Of Year [Text Block] Employee benefit plan schedule of assets held at end of year. Schedule of Assets (Held at End of Year) Investments [Domain] EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment income: EBP, Risk and Uncertainty [Abstract] EBP, Fair Value, Investment, NAV, Redemption, Notice Period Redemption notice period EBP, Debt EBP, Debt, Total Borrowings Net assets available for benefits, at end of year EBP, Net Asset Available for Benefit Net assets available for benefits, at beginning of year Net assets available for benefits EBP, Investment, Fair Value and NAV [Table Text Block] Summary of Fair Value Hierarchy of Plan's Assets and Fair Value of Investments Measured at Net Asset Value as Practical Expedient EBP, Schedule of Asset Held for Investment [Abstract] EBP, Asset Held for Investment, Plan Interest in Master Trust, Participation Status [Extensible Enumeration] Great Gray Trust Company LLC [Member] Great Gray Trust Company LLC. Great Gray Trust Company, LLC Six Year Or More Years [Member] Six year or more years. 6 or More Years EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Current Value EBP, Note Receivable from Participant [Policy Text Block] Notes Receivable from Participants Employee Benefit Plan, Percentage Company Directs Employee benefit plan, percentage company directs. Company directs percentage EBP, Schedule of Asset Held for Investment [Table Text Block] Schedule of Assets (Held at End of Year) EBP, Investment, Purchased, Number of Shares Number of shares purchased MFS Series Trust Fund [Member] MFS Series Trust Fund. MFS Series Trust Fund EBP, Statement of Net Asset Available for Benefit [Table] Employee Benefit Plan, Account Vesting Percentage Employee benefit plan, account vesting percentage. Participant's account balance percentage vested, upon death, disability, or normal retirement (age 65) Document Fiscal Year Focus EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment, Total Net appreciation in fair value of investments EBP, Fair Value, Investment, NAV, Unfunded Commitment Unfunded commitment EBP, Employer Contribution, Participant Compensation Matched, Percentage Percentage of employee's eligible compensation EBP, Statement of Change in Net Asset Available for Benefit [Table] Total assets EBP, Asset Money Market Funds [Member] Money Market Mutual Fund EBP, Plan Number EBP, Investment, Fair Value and NAV [Line Items] Legal Entity [Axis] EBP, Plan Name EBP, Risk and Uncertainty [Line Items] EBP, Asset [Abstract] Assets EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Total investment income EBP, Investment, Fair Value and NAV [Table] EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Participants rollover contributions EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] EBP, Asset Held for Investment Total EBP, Subsequent Event [Line Items] EBP, Tax Status [Text Block] Tax Status EBP, Investment, Sold, Number of Shares Number of shares sold Maximum Maximum [Member] EBP, Other Receivable Dividends and other Fidelity Institutional Asset Management [Member] Fidelity Institutional Asset Management. Fidelity Institutional Asset Management Statistical Measurement [Axis] EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Metlife Metlife [Member] Metlife. EBP 001 [Member] EBP 001. EBP 001 EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Dividends Entity Registrant Name EBP, Receivable Total receivables Interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Employee Benefit Plan Uncertain Tax Positions Taken Employee benefit plan uncertain tax positions taken. Uncertain tax positions Employee Benefit Plan, Eligibility Description Employee benefit plan, eligibility description. Eligibility Safe Harbor Match Safe Harbor Match [Member] Safe Harbor Match member. Employee Benefit Plans, Summary of Six Year Graded Vesting Schedule [Table Text Block] Summary of Six Year Graded Vesting Schedule Employee benefit plans, summary of six year graded vesting schedule, table text block. EBP, Risk and Uncertainty [Text Block] Concentration of Risk Total deductions from net assets EBP, Change in Net Asset Available for Benefit, Decrease Fair Value, Inputs, Level 1 [Member] Level 1 Two Year But Less Than Three Years [Member] Two year but less than three years. 2 Years but less than 3 Years GALLIARD STABLE RETURN FUND E [Member] GALLIARD STABLE RETURN FUND E. Galliard Stable Return Fund E Normal retirement age Employee Benefit Plan, Normal Retirement Age Employee benefit plan, normal retirement age. EBP, Tax Status [Line Items] Entity Tax Identification Number Net increase in net assets available for benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) EBP, Tax Status [Table] Summary of Fair Value of Individual Investments Represents 10% or More of Plan's Net Assets Available for Benefits EBP, Risk and Uncertainty [Table Text Block] Contributions, description Employee Benefit Plan, Contribution, Description Employee benefit plan, contribution, description. EBP, Description, Available [true false] Description available EBP, Asset Held for Investment, Party-in-Interest [true false] GREAT GRAY TR EUROPACGRTH CT. PRINCIPAL SMALLCAP GROWTH R6. TROWEPRICE RETRMNT 2025 TRST K [Member] TROWEPRICE RETRMNT 2035 TRST K. Metropolitan Life Insurance Company [Member] TROWEPRICE RETRMNT 2055 TRST K [Member] TROWEPRICE RETRMNT 2045 TRST K. TROWEPRICE RETRMNT 2020 TRST K [Member] TROWEPRICE RETRMNT 2005 TRST K [Member] McGrath RentCorp common stock. TROWEPRICE RETRMNT 2040 TRST K. TROWEPRICE RETRMNT 2005 TRST K. SS INST US GOV MM ADMIN. Principal funds. PRINCIPAL SMALLCAP GROWTH R6 [Member] Galliard Capital Management. NT CIT S&P 500 INDEX DC NL. FIAM CORE PLUS COM POOL CL I [Member] TROWEPRICE RETRMNT 2025 TRST K. TROWEPRICE RETRMNT 2065 TRST K. Victory Capital [Member] VICTORY SYC SMALL CO OPP R6. GREAT GRAY TR EUROPACGRTH CT [Member] TROWEPRICE RETRMNT 2060 TRST K [Member] NT CIT EXTND MKT IDX DC NL [Member] Victory capital. TROWEPRICE RETRMNT 2050 TRST K. TROWEPRICE RETRMNT 2065 TRST K [Member] MFS LRG CAP VALUE FD CIT CL CT. TROWEPRICE RETRMNT 2045 TRST K [Member] TROWEPRICE RETRMNT 2060 TRST K. SS INST US GOV MM ADMIN [Member] MFS MID CAP VALUE FUND CL CT. TROWEPRICE RETRMNT 2050 TRST K [Member] TROWEPRICE RETRMNT 2020 TRST K. GG CIT III Metlife GAC 25554 J [Member] Harbor Funds [Member] HARTFORD INTL OPPOR HLS IA [Member] TROWEPRICE RETRMNT 2015 TRST K. Principal Funds [Member] HARBOR CAPITAL APPREC CIT CL R. FIAM CORE PLUS COM POOL CL I. TROWEPRICE RETRMNT 2035 TRST K [Member] T Rowe Price. TROWEPRICE RETRMNT BAL TRST K. TROWEPRICE RETRMNT BAL TRST K [Member] MFS MID CAP GROWTH FUND CT. NT CIT ACWI EX US IMI DC NL. TROWEPRICE RETRMNT 2010 TRST K. Harbor Funds. TROWEPRICE RETRMNT 2015 TRST K [Member] T Rowe Price [Member] GG CIT III Metlife GAC 25554 J. NT CIT S And P 500 INDEX DC NL [Member] HARBOR CAPITAL APPREC CIT CL R [Member] McGrath RentCorp Common Stock [Member] VICTORY SYC SMALL CO OPP R6 [Member] MFS MID CAP VALUE FUND CL CT [Member] NT CIT AGGREGATE BD IDX NL. NT CIT ACWI EX US IMI DC NL [Member] Various Investments Including Common Stocks Mutual Funds Money Market Funds And Unit Investment Trusts [Member] TROWEPRICE RETRMNT 2030 TRST K [Member] NT CIT AGGREGATE BD IDX NL [Member] Galliard Capital Management [Member] TROWEPRICE RETRMNT 2040 TRST K [Member] TROWEPRICE RETRMNT 2010 TRST K [Member] Hartford funds. MFS LRG CAP VALUE FD CIT CL CT [Member] Hartford Funds [Member] Metropolitan Life Insurance Company. Various investments including common stocks, mutual funds, money market funds and unit investment trusts. HARTFORD INTL OPPOR HLS IA. NT CIT EXTND MKT IDX DC NL. TROWEPRICE RETRMNT 2030 TRST K. TROWEPRICE RETRMNT 2055 TRST K. MFS MID CAP GROWTH FUND CT [Member]