v3.10.0.1
Document And Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 30, 2018
Document Information [Line Items]    
Entity Registrant Name GENERAC HOLDINGS INC.  
Entity Central Index Key 0001474735  
Trading Symbol gnrc  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Common Stock, Shares Outstanding (in shares)   62,059,983
Document Type 10-Q  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Amendment Flag false