Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	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
Acquisition of business	0	0	0	0	0	0	0	4,125	4,125
Unrealized gain (loss) on interest rate swaps, net of tax	0	0	0	0	0	(5,124)	(5,124)	0	(5,124)
Foreign currency translation adjustment	$ 0	0	$ 0	0	0	(933)	(933)	55	(878)
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)	209,143		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price	$ 2	1,681	$ 0	0	0	0	1,683	0	1,683
Net share settlement of restricted stock awards (in shares)	0		(50,651)
Net share settlement of restricted stock awards	$ 0	0	$ (2,642)	0	0	0	(2,642)	0	(2,642)
Share-based compensation	0	3,594	0	0	0	0	3,594	0	3,594
Redemption value adjustment	0	0	0	0	2,432	0	2,432	0	2,432
Net income attributable to Generac Holdings Inc.	$ 0	0	$ 0	0	44,861	0	44,861		44,861
Net income								643
Net income									45,504
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
Balance (in shares) at Dec. 31, 2019	71,667,726		(9,103,013)
Balance at Dec. 31, 2019	$ 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	(15,813)	(15,813)	0	(15,813)
Foreign currency translation adjustment	$ 0	0	$ 0	0	0	(33,214)	(33,214)	(4)	(33,218)
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price (in shares)	176,949		0
Common stock issued under equity incentive plans, net of shares withheld for employee taxes and strike price	$ 2	755	$ 0	0	0	0	757	0	757
Net share settlement of restricted stock awards (in shares)	0		(66,881)
Net share settlement of restricted stock awards	$ 0	0	$ (6,835)	0	0	0	(6,835)	0	(6,835)
Share-based compensation	0	4,574	0	0	0	0	4,574	0	4,574
Redemption value adjustment	0	0	0	0	(1,522)	0	(1,522)	0	(1,522)
Net income attributable to Generac Holdings Inc.	0	0	0	0	44,460	0	44,460		44,460
Net income								(420)
Net income									44,040
Accounting standard adoption impact	$ 0	0	$ 0	0	(1,147)	0	(1,147)	0	(1,147)
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