Note 7 - Segment Reporting - Net Sales by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net sales	$ 942,698	$ 701,355	$ 2,670,113	$ 1,724,118
Domestic [Member]
Net sales	790,764	606,875	2,267,648	1,443,680
International [Member]
Net sales	151,934	94,480	402,465	280,438
Residential Power Products [Member]
Net sales	608,816	458,877	1,750,957	1,057,848
Residential Power Products [Member] | Domestic [Member]
Net sales	585,150	441,532	1,690,707	1,013,219
Residential Power Products [Member] | International [Member]
Net sales	23,666	17,345	60,250	44,629
Commercial and Industrial Power Products [Member]
Net sales	258,309	176,200	714,994	503,156
Commercial and Industrial Power Products [Member] | Domestic [Member]
Net sales	140,824	108,774	402,357	294,940
Commercial and Industrial Power Products [Member] | International [Member]
Net sales	117,485	67,426	312,637	208,216
Other Products and Services [Member]
Net sales	75,573	66,278	204,162	163,114
Other Products and Services [Member] | Domestic [Member]
Net sales	64,790	56,569	174,584	135,521
Other Products and Services [Member] | International [Member]
Net sales	$ 10,783	$ 9,709	$ 29,578	$ 27,593