Note 13 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income attributable to Generac Holdings Inc.		$ 131,570	$ 114,970	$ 407,599	$ 225,575
Redeemable noncontrolling interest redemption value adjustment		(7,557)	811	(5,687)	(2,281)
Net income attributable to common shareholders		$ 124,013	$ 115,781	$ 401,912	$ 223,294
Weighted average shares, basic (in shares)		62,690,437	62,353,473	62,583,957	62,244,872
Dilutive effect of stock compensation awards (in shares)	[1]	1,517,680	1,407,907	1,562,325	1,301,260
Diluted shares (in shares)		64,208,116	63,761,380	64,146,281	63,546,132
Net income attributable to Generac Holdings Inc. per common share - basic: (in dollars per share)		$ 1.98	$ 1.86	$ 6.42	$ 3.59
Net income attributable to Generac Holdings Inc. per common share - diluted: (in dollars per share)		$ 1.93	$ 1.82	$ 6.27	$ 3.51

[1] There were no awards with an anti-dilutive impact for the three and nine months ended September 30, 2021 and 2020.