Note 13 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income attributable to Generac Holdings Inc.		$ 53,261	$ 25,291	$ 86,906	$ 37,466
Redeemable noncontrolling interest redemption value adjustment		(2,305)	295	(9,970)	909
Net income attributable to common shareholders		$ 50,956	$ 25,586	$ 76,936	$ 38,375
Weighted average shares, basic (in shares)		61,534,423	62,146,393	61,696,014	62,260,170
Dilutive effect of stock compensation awards (in shares)	[1]	520,024	489,044	563,698	589,707
Diluted shares (in shares)		62,054,447	62,635,437	62,259,712	62,849,877
Basic (in dollars per share)		$ 0.83	$ 0.41	$ 1.25	$ 0.62
Diluted (in dollars per share)		$ 0.82	$ 0.41	$ 1.24	$ 0.61

[1] Excludes approximately 142,600 and 279,200 stock options for the three months ended June 30, 2018 and 2017, respectively, as the impact of such awards was anti-dilutive. Excludes approximately 81,800 and 193,200 stock options for the six months ended June 30, 2018 and 2017, respectively, as the impact of such awards was anti-dilutive. Excludes approximately 7,000 shares of restricted stock for the three months ended June 30, 2017, as the impact of such awards was anti-dilutive.