Note 12 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (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
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
Redemption value adjustment										(909)
Net income attributable to common shareholders										$ 97,879	$ 77,747	$ 174,613
Weighted average shares, basic (in shares)										64,905,793	68,096,051	68,538,248
Dilutive effect of stock compensation awards (in shares)	[1]									476,981	1,104,246	1,632,796
Diluted shares (in shares)										65,382,774	69,200,297	70,171,044
Basic (in dollars per share)		$ 0.64	$ 0.41	$ 0.32	$ 0.15	$ 0.14	$ 0.50	$ 0.22	$ 0.29	$ 1.51	$ 1.14	$ 2.55
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

[1] Excludes approximately 15,800, 161,400 and 81,600 stock options for the years ended December 31, 2016, 2015 and 2014, respectively, as the impact of such awards was anti-dilutive. Excludes approximately 1,000 shares of restricted stock for the year ended December 31, 2015, as the impact of such awards was anti-dilutive.