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Summary of Significant Accounting Policies - Estimated Useful Lives and Residual Values of Company's Rental Equipment (Detail)	12 Months Ended
	Dec. 31, 2014
Relocatable modular buildings [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	18 years
Percentage residual value property subject to or available for operating lease	50.00%mgrc_PercentageResidualValuePropertySubjectToOrAvailableForOperatingLease / us-gaap_PropertyPlantAndEquipmentByTypeAxis = mgrc_RelocatableModularBuildingsMember
Relocatable modular accessories [Member]
Property, Plant and Equipment [Line Items]
Percentage residual value property subject to or available for operating lease	0.00%mgrc_PercentageResidualValuePropertySubjectToOrAvailableForOperatingLease / us-gaap_PropertyPlantAndEquipmentByTypeAxis = mgrc_RelocatableModularAccessoriesMember
Portable storage containers [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	25 years
Percentage residual value property subject to or available for operating lease	62.50%mgrc_PercentageResidualValuePropertySubjectToOrAvailableForOperatingLease / us-gaap_PropertyPlantAndEquipmentByTypeAxis = mgrc_PortableStorageContainersMember
Electronic test equipment and accessories [Member]
Property, Plant and Equipment [Line Items]
Percentage residual value property subject to or available for operating lease	0.00%mgrc_PercentageResidualValuePropertySubjectToOrAvailableForOperatingLease / us-gaap_PropertyPlantAndEquipmentByTypeAxis = mgrc_ElectronicTestEquipmentAndAccessoriesMember
Liquid and solid containment tanks and boxes and accessories [Member]
Property, Plant and Equipment [Line Items]
Percentage residual value property subject to or available for operating lease	0.00%mgrc_PercentageResidualValuePropertySubjectToOrAvailableForOperatingLease / us-gaap_PropertyPlantAndEquipmentByTypeAxis = mgrc_LiquidAndSolidContainmentTanksAndAccessoriesMember
Minimum [Member] | Relocatable modular accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	3 years
Minimum [Member] | Electronic test equipment and accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	1 year
Minimum [Member] | Liquid and solid containment tanks and boxes and accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	10 years
Maximum [Member] | Relocatable modular accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	18 years
Maximum [Member] | Electronic test equipment and accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	8 years
Maximum [Member] | Liquid and solid containment tanks and boxes and accessories [Member]
Property, Plant and Equipment [Line Items]
Property subject to or available for operating lease useful life	20 years

X

- Definition

Percentage residual value property subject to or available for operating lease.

+ References

No definition available.

+ Details

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X

- Definition

Property subject to or available for operating lease useful life.

+ References

No definition available.

+ Details

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X

- Details

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- Details

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- Details

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X

- Details

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Balance Type:
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X

- Details

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X

- Details

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X

- Details

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- Details

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