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v3.19.3.a.u2

Note 2 - Summary of Accounting Policies - Property and Equipment Estimated Useful Lives (Details) | 12 Months Ended
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Dec. 31, 2019
Land Improvements [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 8 years
Land Improvements [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 20 years
Building and Building Improvements [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 10 years
Building and Building Improvements [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 40 years
Machinery and Equipment [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 3 years
Machinery and Equipment [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 15 years
Dies and Tools [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 3 years
Dies and Tools [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 10 years
Vehicles [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 3 years
Vehicles [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 6 years
Office Equipment [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 3 years
Office Equipment [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 15 years
Leasehold Improvements [Member] | Minimum [Member] |
Property and equipment, estimated useful lives (Year) | 2 years
Leasehold Improvements [Member] | Maximum [Member] |
Property and equipment, estimated useful lives (Year) | 20 years

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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LandImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=gnrc_DiesAndToolsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_OfficeEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |