Note 1 - Description of Business (Details Textual)	12 Months Ended
Dec. 31, 2018
Pramac [Member]
Number of Countries Where Product is Sold by Subsidiary	150

Represents the number of countries in where the subsidiary sells its products.

No definition available.

Name:	gnrc_NumberOfCountriesWhereProductIsSoldBySubsidiary
Namespace Prefix:	gnrc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration