Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Excess Purchase Price over Predecessor Basis [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Parent [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Noncontrolling Interest [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [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
Change in noncontrolling interest share										0	0	0	0	0	0	0	(154)	(154)
Net unrealized gain (loss) on derivatives										$ 0	0	$ 0	0	0	(13,855)	(13,855)	0	(13,855)
Foreign currency translation adjustment															2,210	2,210	(30)	2,180
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)										481,308
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price										$ 5	6,056					6,061		6,061
Net share settlement of restricted stock awards (in shares)												(55,953)
Net share settlement of restricted stock awards												$ (3,078)				(3,078)		(3,078)
Cash dividends paid to noncontrolling interest of subsidiary										0	0	0	0	0	0	0	(285)	(285)
Share-based compensation										0	16,694	0	0	0	0	16,694	0	16,694
Pension liability adjustment and settlement, net of tax										0	0	0	0	0	10,541	10,541	0	10,541
Redemption value adjustment										0	0	0	0	1,253	0	1,253	0	1,253
Net income attributable to Generac Holdings Inc.										$ 0	0	$ 0	0	252,007	0	252,007		252,007
Net income																	226
Net income																		252,233
Balance (in shares) at Dec. 31, 2019										71,667,726		(9,103,013)
Balance at Dec. 31, 2019	$ 0	$ 0	$ 0	$ 0	$ (1,147)	$ 0	$ (1,147)	$ 0	$ (1,147)	$ 717	498,866	$ (324,551)	(202,116)	1,084,383	(24,917)	1,032,382	469	1,032,851
Net unrealized gain (loss) on derivatives										0	0	0	0	0	(14,285)	(14,285)	0	(14,285)
Foreign currency translation adjustment										$ 0	0	$ 0	0	0	4,948	4,948	(29)	4,919
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)										356,603		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price										$ 4	5,793	$ 0	0	0	0	5,797	0	5,797
Net share settlement of restricted stock awards (in shares)										0		(70,718)
Net share settlement of restricted stock awards										$ 0	0	$ (7,613)	0	0	0	(7,613)	0	(7,613)
Share-based compensation										0	20,882	0	0	0	0	20,882	0	20,882
Pension liability adjustment and settlement, net of tax																		0
Redemption value adjustment										0	0	0	0	(1,247)	0	(1,247)	0	(1,247)
Net income attributable to Generac Holdings Inc.										$ 0	0	$ 0	0	350,576	0	350,576		350,576
Net income																	(529)
Net income																		350,047
Balance (in shares) at Dec. 31, 2020										72,024,329		(9,173,731)
Balance at Dec. 31, 2020										$ 721	525,541	$ (332,164)	(202,116)	1,432,565	(34,254)	1,390,293	(89)	1,390,204
Change in noncontrolling interest share										0	0	0	0	0	0	0	(96)	(96)
Net unrealized gain (loss) on derivatives															20,529	20,529		20,529
Foreign currency translation adjustment										$ 0	0	$ 0	0	0	(41,030)	(41,030)	(3)	(41,033)
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)										331,048		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price										$ 3	7,073	$ 0	0	0	0	7,076	0	7,076
Net share settlement of restricted stock awards (in shares)										0		(80,583)
Net share settlement of restricted stock awards										$ 0	0	$ (27,223)	0	0	0	(27,223)	0	(27,223)
Share-based compensation										0	23,954	0	0	0	0	23,954	0	23,954
Pension liability adjustment and settlement, net of tax																		0
Redemption value adjustment										0	0	0	0	(17,102)	0	(17,102)	0	(17,102)
Net income attributable to Generac Holdings Inc.										$ 0	0	0	0	550,494	0	550,494		550,494
Net income																	501
Net income																		550,995
Common stock issued for business combination (in shares)										30,640
Common stock issued for business combination										$ 1	12,000	$ 0	0	0	0	12,001	0	12,001
Treasury stock issued for business combination (in shares)										0		937,283
Treasury stock issued for business combination										$ 0	384,371	$ 36,403	0	0	0	420,774	0	420,774
Stock repurchases (in shares)										0		(350,000)
Stock repurchases										$ 0	0	$ (125,992)	0	0	0	(125,992)	0	(125,992)
Balance (in shares) at Dec. 31, 2021										72,386,017		(8,667,031)
Balance at Dec. 31, 2021										$ 725	$ 952,939	$ (448,976)	$ (202,116)	$ 1,965,957	$ (54,755)	$ 2,213,774	$ 313	$ 2,214,087