Note 23 - Quarterly FInancial Information (Unaudited) (Details) - Quarterly Financial Information (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Electricity	$ 93,286	$ 102,506	$ 91,692	$ 94,817	$ 84,742	$ 88,994	$ 87,713	$ 68,298	$ 382,301	$ 329,747	$ 314,894
Product	55,957	37,736	35,911	47,619	46,163	41,755	64,966	50,608	177,223	203,492	186,879
Total revenues	149,243	140,242	127,603	142,436	130,905	130,749	152,679	118,906	559,524	533,239	501,773
Cost of revenues:
Electricity	60,547	61,727	67,322	57,034	57,789	61,356	58,641	55,088	246,630	232,874	237,415
Product	33,836	23,040	20,324	31,943	30,212	29,637	43,657	37,041	109,143	140,547	135,346
Total cost of revenues	94,383	84,767	87,646	88,977	88,001	90,993	102,298	92,129	355,773	373,421	372,761
Gross margin	54,860	55,475	39,957	53,459	42,904	39,756	50,381	26,777	203,751	159,818	129,012
Operating expenses:
Research and development expenses	388	250	232	(87)	1,519	838	1,608	1,000	783	4,965	6,108
Selling and marketing expenses	4,572	4,258	3,216	3,379	6,752	2,575	3,777	11,509	15,425	24,613	15,718
General and administrative expenses	7,767	7,179	6,072	7,596	8,924	6,546	7,134	6,584	28,614	29,188	28,066
Write-off of unsuccessful exploration activities	7,332		8,107		4,094				15,439	4,094	2,639
Operating income	34,801	43,788	22,330	42,571	21,615	29,797	37,862	7,684	143,490	96,958	(159,896)
Other income (expense):
Interest income	76	35	90	111	462	742	87	41	312	1,332	1,201
Interest expense, net	(19,570)	(22,494)	(22,072)	(20,518)	(21,950)	(18,459)	(17,504)	(15,863)	(84,654)	(73,776)	(64,069)
Foreign currency translation and transaction gains (losses)	(2,200)	(2,946)	(55)	(638)	1,241	1,258	904	1,682	(5,839)	5,085	242
Income attributable to sale of tax benefits	5,809	5,487	6,130	6,717	5,603	5,027	5,783	3,532	24,143	19,945	10,127
Gain from sale of property, plant and equipment			7,628						7,628
Other non-operating income (expense), net	107	243	343	63	9	137	29	1,417	756	1,592	590
Income (loss) from continuing operations, before income taxes and equity in income of investees	19,023	24,113	14,394	28,306	6,980	18,502	27,161	(1,507)	85,836	51,136	(211,805)
Income tax benefit (provision)	(9,877)	(6,444)	(4,967)	(6,320)	1,476	(5,201)	(5,780)	(4,047)	(27,608)	(13,552)	(1,827)
Equity in income (losses) of investees	(2,003)	(899)	(114)	(197)	(101)	(158)	9		(3,213)	(250)	(2,522)
Income (loss) from continuing operations	7,143	16,770	9,313	21,789	8,355	13,143	21,390	(5,554)	55,015	37,334	(216,154)
Discontinued operations:
Income from discontinued operations (including gain on disposal of $0, $3,646, $0, $0, $0, $0, $0, and $0, respectively)							4,480	831		5,311	4,811
Total income from discontinued operations							4,117	580		4,697	3,547
Net income (loss)	7,143	16,770	9,313	21,789	8,355	13,143	25,507	(4,974)	55,015	42,031	(212,607)
Net loss (income) attributable to noncontrolling interest	(163)	(256)	(177)	(237)	(193)	(193)	(322)	(85)	(833)	(793)	(414)
Net income (loss) attributable to the Company's stockholders	6,980	16,514	9,136	21,552	8,162	12,950	25,185	(5,059)	54,182	41,238	(213,021)
Basic:
Income (loss) from continuing operations (in Dollars per share)	$ 0.15	$ 0.37	$ 0.20	$ 0.47	$ 0.18	$ 0.29	$ 0.46	$ (0.12)	$ 1.19	$ 0.81	$ (4.77)
Discontinued operations (in Dollars per share)							$ 0.09	$ 0.01		$ 0.10	$ 0.08
Net income (loss) (in Dollars per share)	$ 0.15	$ 0.37	$ 0.20	$ 0.47	$ 0.18	$ 0.29	$ 0.55	$ (0.11)	$ 1.19	$ 0.91	$ (4.69)
Diluted:
Income (loss) from continuing operations (in Dollars per share)	$ 0.15	$ 0.36	$ 0.20	$ 0.47	$ 0.18	$ 0.28	$ 0.46	$ (0.12)	$ 1.18	$ 0.81	$ (4.77)
Discontinued operations (in Dollars per share)							$ 0.09	$ 0.01		$ 0.10	$ 0.08
Net income (loss) (in Dollars per share)	$ 0.15	$ 0.36	$ 0.20	$ 0.47	$ 0.19	$ 0.28	$ 0.55	$ (0.11)	$ 1.18	$ 0.91	$ (4.69)
Weighted average number of shares used in computation of earnings (loss) per share attributable to the Company's stockholders:
Basic (in Shares)	45,537	45,690	45,606	45,479	45,461	45,438	45,431	45,431	45,508	45,440	45,431
Diluted (in Shares)	46,018	46,102	45,963	45,660	45,610	45,494	45,448	45,431	45,859	45,475	45,431
Discontinued Operations [Member]
Other income (expense):
Income tax benefit (provision)							$ (363)	$ (251)		$ (614)	$ (1,264)