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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income attributable to Generac Holdings Inc.		$ 75,776	$ 39,435	$ 162,682	$ 76,901
Redeemable noncontrolling interest redemption value adjustment		(6,912)		(16,882)	909
Net income attributable to common shareholders		$ 68,864	$ 39,435	$ 145,800	$ 77,810
Weighted average shares, basic (in shares)		61,579,564	61,758,190	61,659,817	62,094,807
Dilutive effect of stock compensation awards (in shares)	[1]	640,734	558,598	606,323	608,462
Diluted shares (in shares)		62,220,298	62,316,788	62,266,140	62,703,269
Basic (in dollars per share)		$ 1.12	$ 0.64	$ 2.36	$ 1.25
Diluted (in dollars per share)		$ 1.11	$ 0.63	$ 2.34	$ 1.24

[1] Excludes approximately 38,900 and 146,000 stock options for the three month periods ended September 30, 2018 and 2017, respectively, as the impact of such awards was anti-dilutive. Excludes approximately 48,200 and 188,800 stock options for the nine month periods ended September 30, 2018 and 2017, respectively, as the impact of such awards was anti-dilutive.