Note 18 - Business Segments - Summarized Financial Information Concerning Reportable Segments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue	[1]	$ 663,084	$ 705,342	$ 746,044
Depreciation and amortization expense		182,972	156,612	148,761
Operating income (loss)		169,357	214,013	193,796
Segment assets at period end	[2],[3]	4,425,678	3,888,987	3,250,494
Expenditures for long-lived assets		419,272	320,738	279,986
Segment Reconciling Items [Member]
Revenue		0	0	0
Segment assets at period end		105,886	98,217	81,140
Electricity Segment [Member]
Revenue		585,771	541,393	540,333
Depreciation and amortization expense		164,490	144,357	138,426
Operating income (loss)		171,550	205,256	177,192
Segment assets at period end	[2],[3]	4,142,341	3,607,384	3,044,909
Expenditures for long-lived assets		383,307	267,843	259,898
Electricity Segment [Member] | Segment Reconciling Items [Member]
Revenue		0	0	0
Segment assets at period end		105,886	98,217	81,140
Product Segment [Member]
Revenue		46,920	148,125	191,009
Depreciation and amortization expense		7,719	6,010	5,308
Operating income (loss)		(3,641)	13,145	23,180
Segment assets at period end	[2],[3]	113,817	145,911	126,018
Expenditures for long-lived assets		10,687	18,011	9,156
Product Segment [Member] | Segment Reconciling Items [Member]
Revenue		129,589	113,200	84,614
Segment assets at period end		0	0	0
Other Segments [Member]
Revenue		30,393	15,824	14,702
Depreciation and amortization expense		10,763	6,245	5,027
Operating income (loss)		1,448	(4,388)	(6,576)
Segment assets at period end	[2],[3]	169,520	135,692	79,567
Expenditures for long-lived assets		25,278	34,884	10,932
Other Segments [Member] | Segment Reconciling Items [Member]
Revenue		0	0	0
Segment assets at period end		0	0	0
UNITED STATES
Revenue	[1],[4]	440,110	363,023	377,956
UNITED STATES | Electricity Segment [Member]
Revenue	[4]	404,303	341,399	333,797
UNITED STATES | Product Segment [Member]
Revenue	[4]	5,414	5,800	30,562
UNITED STATES | Other Segments [Member]
Revenue	[4]	30,393	15,824	13,597
Non-US [Member]
Revenue	[5]	222,974	342,319	368,088
Non-US [Member] | Electricity Segment [Member]
Revenue	[5]	181,468	199,994	206,536
Non-US [Member] | Product Segment [Member]
Revenue	[5]	41,506	142,325	160,447
Non-US [Member] | Other Segments [Member]
Revenue	[5]	$ 0	$ 0	$ 1,105

[1] Revenues as reported in the geographic area in which they originate.

[2] Electricity segment assets include goodwill in the amount of $85.3 million, $20.5 million and $20.1 million as of December 31, 2021, 2020 and 2019, respectively, $65.4 million of which was added in the third quarter of 2021 as a result of the Terra-Gen Transaction as further described under Note 2 to the consolidated financial statements. Energy Storage segment assets include goodwill in the amount of $4.6 million, $4.1 million and $0.0 million as of December 31, 2021, 2020 and 2019, respectively. No goodwill is included in the Product segment assets as of December 31, 2021, 2020 and 2019.

[3] Including unconsolidated investments

[4] Electricity segment revenues in the United States are all accounted under lease accounting, except for $83.4 million, $68.1 million and $61.3 million for the years 2021, 2020 and 2019, which are accounted under ASC 606. Product and Energy Storage segment revenues in the United States are accounted under ASC 606, as further described under Note 1 to the consolidated financial statements.

[5] Electricity segment revenues in foreign countries are all accounted under lease accounting. Product and Energy Storage segment revenues in foreign countries are accounted under ASC 606 as further described under Note 1 to the consolidated financial statements.