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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 Segment Product | Dec. 31, 2013 | Dec. 31, 2012
Accounting Policies [Abstract] |  |  |
Number of products | 3 mgrc_NumberOfProducts |  |
Number of reportable segments | 4 us-gaap_NumberOfReportableSegments |  |
Impairments of long-lived assets | $ 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse | $ 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse | $ 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Period for warranties for rental equipment | 90 days |  |
Period for warranties for equipment manufactured | 1 year |  |
Property, plant and equipment depreciation expenses | 7,600,000 us-gaap_Depreciation | 7,800,000 us-gaap_Depreciation | 7,800,000 us-gaap_Depreciation
Capitalized in internal use of software | 400,000 us-gaap_CapitalizedComputerSoftwareNet | 3,500,000 us-gaap_CapitalizedComputerSoftwareNet |
Total advertising expenses | 2,400,000 us-gaap_AdvertisingExpense | 2,400,000 us-gaap_AdvertisingExpense | 2,500,000 us-gaap_AdvertisingExpense
Deferred tax assets, valuation allowance | 0 us-gaap_DeferredTaxAssetsValuationAllowance |  |
Estimated useful life (In years), Customer relationships | 11 years |  |
Goodwill and trade name intangible assets | 33,500,000 mgrc_IndefiniteLivedIntangibleAssetsIncludingGoodwill | 33,400,000 mgrc_IndefiniteLivedIntangibleAssetsIncludingGoodwill |
Goodwill and intangible assets impairment charge | 0 us-gaap_GoodwillAndIntangibleAssetImpairment | 0 us-gaap_GoodwillAndIntangibleAssetImpairment | 0 us-gaap_GoodwillAndIntangibleAssetImpairment
Unbilled receivables related to end-of-lease services | 21,100,000 us-gaap_UnbilledReceivablesCurrent | 18,900,000 us-gaap_UnbilledReceivablesCurrent |
Period for credit risk identified | 30 days |  |
Estimated fair value notes payable | 122,900,000 us-gaap_NotesPayableFairValueDisclosure | 104,600,000 us-gaap_NotesPayableFairValueDisclosure |
Recorded fair value of notes payable | $ 120,000,000 mgrc_RecordedFairValueOfNotesPayable | $ 100,000,000 mgrc_RecordedFairValueOfNotesPayable |

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- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 + Details
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