Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Excess Purchase Price over Predecessor Basis [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2018				71,186,418		(9,047,060)
Balance at Dec. 31, 2018				$ 712	$ 476,116	$ (321,473)	$ (202,116)	$ 831,123	$ (23,813)	$ 760,549	$ 712	$ 761,261
Unrealized gain (loss) on interest rate swaps, net of tax				0	0	0	0	0	(12,177)	(12,177)	0	(12,177)
Foreign currency translation adjustment				$ 0	0	$ 0	0	0	2,159	2,159	38	2,197
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)				284,923		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price				$ 3	1,659	$ 0	0	0	0	1,662	0	1,662
Net share settlement of restricted stock awards (in shares)				0		(51,234)
Net share settlement of restricted stock awards				$ 0	0	$ (2,676)	0	0	0	(2,676)	0	(2,676)
Share-based compensation				0	7,928	0	0	0	0	7,928	0	7,928
Redemption value adjustment				0	0	0	0	1,676	0	1,676	0	1,676
Net income attributable to Generac Holdings Inc.				0	0	0	0	106,819	0	106,819		106,819
Net income											481
Net income												107,300
Cash dividends paid to noncontrolling interest of subsidiary				0	0	0	0	0	0	0	(285)	(285)
Acquisition of business				$ 0	0	$ 0	0	0	0	0	4,125	4,125
Balance (in shares) at Jun. 30, 2019				71,471,341		(9,098,294)
Balance at Jun. 30, 2019				$ 715	485,703	$ (324,149)	(202,116)	939,618	(33,831)	865,940	5,071	871,011
Balance (in shares) at Mar. 31, 2019				71,395,561		(9,097,711)
Balance at Mar. 31, 2019				$ 714	481,391	$ (324,115)	(202,116)	878,416	(29,870)	804,420	5,535	809,955
Unrealized gain (loss) on interest rate swaps, net of tax				0	0	0	0	0	(7,053)	(7,053)	0	(7,053)
Foreign currency translation adjustment				$ 0	0	$ 0	0	0	3,092	3,092	(17)	3,075
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)				75,780		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price				$ 1	(22)	$ 0	0	0	0	(21)	0	(21)
Net share settlement of restricted stock awards (in shares)				0		(583)
Net share settlement of restricted stock awards				$ 0	0	$ (34)	0	0	0	(34)	0	(34)
Share-based compensation				0	4,334	0	0	0	0	4,334	0	4,334
Redemption value adjustment				0	0	0	0	(756)	0	(756)	0	(756)
Net income attributable to Generac Holdings Inc.				0	0	0	0	61,958	0	61,958		61,958
Net income											(162)
Net income												61,796
Cash dividends paid to noncontrolling interest of subsidiary				$ 0	0	$ 0	0	0	0	0	(285)	(285)
Balance (in shares) at Jun. 30, 2019				71,471,341		(9,098,294)
Balance at Jun. 30, 2019				$ 715	485,703	$ (324,149)	(202,116)	939,618	(33,831)	865,940	5,071	871,011
Balance (in shares) at Dec. 31, 2019				71,667,726		(9,103,013)
Balance at Dec. 31, 2019	$ (1,147)	$ (1,147)	$ (1,147)	$ 717	498,866	$ (324,551)	(202,116)	1,084,383	(24,917)	1,032,382	469	1,032,851
Unrealized gain (loss) on interest rate swaps, net of tax				0	0	0	0	0	(19,409)	(19,409)	0	(19,409)
Foreign currency translation adjustment				$ 0	0	$ 0	0	0	(28,200)	(28,200)	(2)	(28,202)
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)				292,341		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price				$ 3	3,478	$ 0	0	0	0	3,481	0	3,481
Net share settlement of restricted stock awards (in shares)				0		(67,149)
Net share settlement of restricted stock awards				$ 0	0	$ (6,864)	0	0	0	(6,864)	0	(6,864)
Share-based compensation				0	9,974	0	0	0	0	9,974	0	9,974
Redemption value adjustment				0	0	0	0	(3,092)	0	(3,092)	0	(3,092)
Net income attributable to Generac Holdings Inc.				$ 0	0	$ 0	0	110,605	0	110,605		110,605
Net income											(922)
Net income												109,683
Balance (in shares) at Jun. 30, 2020				71,960,067		(9,170,162)
Balance at Jun. 30, 2020				$ 720	512,318	$ (331,415)	(202,116)	1,190,749	(72,526)	1,097,730	(455)	1,097,275
Balance (in shares) at Mar. 31, 2020				71,844,675		(9,169,894)
Balance at Mar. 31, 2020				$ 719	504,195	$ (331,386)	(202,116)	1,126,174	(73,944)	1,023,642	45	1,023,687
Unrealized gain (loss) on interest rate swaps, net of tax				0	0	0	0	0	(3,596)	(3,596)	0	(3,596)
Foreign currency translation adjustment				$ 0	0	$ 0	0	0	5,014	5,014	2	5,016
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)				115,392		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price				$ 1	2,723	$ 0	0	0	0	2,724	0	2,724
Net share settlement of restricted stock awards (in shares)				0		(268)
Net share settlement of restricted stock awards				$ 0	0	$ (29)	0	0	0	(29)	0	(29)
Share-based compensation				0	5,400	0	0	0	0	5,400	0	5,400
Redemption value adjustment				0	0	0	0	(1,570)	0	(1,570)	0	(1,570)
Net income attributable to Generac Holdings Inc.				$ 0	0	$ 0	0	66,145	0	66,145		66,145
Net income											(502)
Net income												65,643
Balance (in shares) at Jun. 30, 2020				71,960,067		(9,170,162)
Balance at Jun. 30, 2020				$ 720	$ 512,318	$ (331,415)	$ (202,116)	$ 1,190,749	$ (72,526)	$ 1,097,730	$ (455)	$ 1,097,275