Note 3 - Acquisitions - Unaudited Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
As reported	$ 417,421	$ 373,121	$ 367,376	$ 286,535	$ 357,830	$ 359,291	$ 288,360	$ 311,818	$ 1,444,453	$ 1,317,299	$ 1,460,919
Pro forma									1,473,799	1,556,459	1,776,843
Net income attributable to Generac Holdings Inc.	$ 41,509	$ 26,183	$ 20,888	$ 10,208	$ 9,182	$ 34,036	$ 14,844	$ 19,685	98,788	77,747	174,613
Pro forma									$ 100,907	$ 78,618	$ 174,926
As reported (in dollars per share)	$ 0.64	$ 0.40	$ 0.31	$ 0.15	$ 0.14	$ 0.49	$ 0.21	$ 0.28	$ 1.50	$ 1.12	$ 2.49
Pro forma (in dollars per share)									$ 1.53	$ 1.14	$ 2.49