Note 7 - Variable Interest Entities (Details) - Assets and Liabilities for the Company's 2015 Variable Interest Entity - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Restricted cash and cash equivalents		$ 49,503	$ 93,248
Property, plant and equipment, net		1,559,335	1,437,637
Construction-in-process		248,835	296,722
Total assets	[1]	2,293,044	2,121,556	$ 2,159,433
Liabilities:
Accounts payable and accrued expenses		91,955	88,276
Long-term debt		920,465
Other long-term liabilities		1,776	2,956
Total liabilities		1,209,170	1,334,810
Variable Interest Entity, Primary Beneficiary [Member] | Project Debt [Member]
Assets:
Restricted cash and cash equivalents		49,503	87,832
Other current assets		114,500	72,091
Unconsolidated investments		0
Property, plant and equipment, net		1,310,027	1,160,559
Construction-in-process		127,825	161,534
Other long-term assets		44,279	51,264
Total assets		1,646,134	1,533,280
Liabilities:
Accounts payable and accrued expenses		11,404	14,266
Long-term debt		648,028	685,248
Other long-term liabilities		78,843	91,254
Total liabilities		738,275	790,768
Variable Interest Entity, Primary Beneficiary [Member] | Power Purchase Agreements [Member]
Assets:
Other current assets		4,044	4,496
Unconsolidated investments		0
Property, plant and equipment, net		171,231	178,783
Construction-in-process		1,340	472
Other long-term assets		(1)	(1)
Total assets		176,614	183,750
Liabilities:
Accounts payable and accrued expenses		2,931	2,990
Other long-term liabilities		5,358	6,885
Total liabilities		$ 8,289	$ 9,875

[1] Including unconsolidated investments