Note 5 - Variable Interest Entities (Details) - Assets and Liabilities for the Company's 2013 Variable Interest Entity (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Assets:
Restricted cash, cash equivalents and marketable securities	$ 93,248		$ 51,065
Property, plant and equipment, net	1,437,637		1,452,336
Construction-in-process	296,722		288,827
Total assets	2,121,556	[1]	2,159,433	[1]
Liabilities:
Accounts payable and accrued expenses	88,276		98,047
Other long-term liabilities	2,956		3,529
Total liabilities	1,334,810		1,414,322
Project Debt [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Restricted cash, cash equivalents and marketable securities	87,832		48,276
Other current assets	72,091		66,672
Property, plant and equipment, net	1,160,559		1,190,467
Construction-in-process	161,534		136,486
Other long-term assets	51,264		56,601
Total assets	1,533,280		1,498,502
Liabilities:
Accounts payable and accrued expenses	14,266		16,087
Long-term debt			632,906
Other long-term liabilities	91,254		103,538
Total liabilities	790,768		752,531
Power Purchase Agreements [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Other current assets	4,496		5,459
Property, plant and equipment, net	178,783		190,616
Construction-in-process	472		461
Other long-term assets	(1)		267
Total assets	183,750		196,803
Liabilities:
Accounts payable and accrued expenses	2,990		2,608
Other long-term liabilities	6,885		5,948
Total liabilities	9,875		8,556
Less than Majority-owned Subsidiaries [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Construction-in-process			11,055
Total assets			$ 11,055

[1] Including unconsolidated investments