XML 74 R56.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Income Taxes - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Operating Loss Carryforwards [Line Items] |  |  |
Federal corporate tax rate | 21.00% | 21.00% | 35.00%
Deferred tax liability related to foreign earnings | $ 0 |  |
Excess tax shortfall (benefit) from exercise of share-based awards | $ (2,100,000) | $ (2,000,000.0) | $ (900,000)
Likelihood percentage of being realized upon ultimate settlement with the relevant tax authority | 50.00% |  |
Unrecognized tax benefits | $ 0 | 0 |
Changes in unrecognized benefits | 0 | $ 0 | $ 0
Foreign [Member] |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Net operating losses carryforwards | $ 600,000 |  |
Net operating losses carryforwards, expiration year | 2023 |  |

X
- Definition Operating loss carryforwards expiration year. + References No definition available. + Details
Name: | mgrc_OperatingLossCarryforwardsExpirationYear
Namespace Prefix: | mgrc_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax benefit likelihood percentage. + References No definition available. + Details
Name: | mgrc_TaxBenefitLikelihoodPercentage
Namespace Prefix: | mgrc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax cuts and jobs act of 2017 incomplete accounting accumulated earnings of foreign subsidiary provisional unrecognized deferred tax liability. + References No definition available. + Details
Name: | mgrc_TaxCutsAndJobsActOf2017IncompleteAccountingAccumulatedEarningsOfForeignSubsidiaryProvisionalUnrecognizedDeferredTaxLiability
Namespace Prefix: | mgrc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Excess tax shortfall (benefit) from exercise of stock options. + References No definition available. + Details
Name: | mgrc_TaxExpenseBenefitFromExercisingOfShareBasedCompensation
Namespace Prefix: | mgrc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
Name: | us-gaap_OperatingLossCarryforwards
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_OperatingLossCarryforwardsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 10B -URI http://asc.fasb.org/extlink&oid=116821951&loc=SL37586934-109318 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |