Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 19, 2020	Jun. 28, 2019
Document Information [Line Items]
Entity Central Index Key	0001474735
Entity Registrant Name	GENERAC HOLDINGS INC.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-34627
Entity Incorporation, State or Country Code	DE
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
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 4,191,188,195
Entity Common Stock, Shares Outstanding		62,567,525