| Document And Entity Information | Oct. 24, 2019 |
| Document Information [Line Items] | |
| Entity Registrant Name | Generac Holdings Inc. |
| Document Type | 8-K |
| Document Period End Date | Oct. 24, 2019 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-34627 |
| Entity Tax Identification Number | 20-5654756 |
| Entity Address, Address Line One | S45 W29290 Hwy 59 |
| Entity Address, City or Town | Waukesha |
| Entity Address, State or Province | WI |
| Entity Address, Postal Zip Code | 53189 |
| City Area Code | (262) |
| Local Phone Number | 544-4811 |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | GNRC |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001474735 |
