Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Total, net		$ (8,515)	$ 874
Cash equivalents (including restricted cash accounts)		17,378	14,922
Derivative Asset, Current	[1]	251
Reported Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,088	1,443
Reported Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(25,486)	(11,581)
Reported Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Liability, Current	[3]		(481)
Derivative Asset, Current	[3]	2,007
Reported Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[2]	(3,753)	(3,429)
Estimate of Fair Value Measurement [Member]
Total, net		(8,515)	874
Cash equivalents (including restricted cash accounts)		17,378	14,922
Derivative Asset, Current	[1]	251
Estimate of Fair Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,088	1,443
Estimate of Fair Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(25,486)	(11,581)
Estimate of Fair Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Liability, Current	[3]		(481)
Derivative Asset, Current	[3]	2,007
Estimate of Fair Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[2]	(3,753)	(3,429)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Total, net		17,378	14,922
Cash equivalents (including restricted cash accounts)		17,378	14,922
Derivative Asset, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Currency Forward Contracts [Member]
Derivative Liability, Current	[3]
Derivative Asset, Current	[3]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Warrant [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Total, net		2,258	(481)
Cash equivalents (including restricted cash accounts)
Derivative Asset, Current	[1]	251
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Currency Forward Contracts [Member]
Derivative Liability, Current	[3]		(481)
Derivative Asset, Current	[3]	2,007
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Warrant [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Total, net		(28,151)	(13,567)
Cash equivalents (including restricted cash accounts)
Derivative Asset, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,088	1,443
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(25,486)	(11,581)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Currency Forward Contracts [Member]
Derivative Liability, Current	[3]
Derivative Asset, Current	[3]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Derivative Liability, Current	[2]	$ (3,753)	$ (3,429)

[1] These amounts relate to natural gas put options, valued primarily based on observable inputs, including spot prices on related commodity indices, and are included within Prepaid expenses and other on June 30, 2017 in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

[2] These amounts relate to contingent receivables and payables relating to the Viridity acquisition and Guadeloupe power plant purchase transaction, valued primarily based on unobservable inputs and are included within Prepaid expenses and other, Accounts payable and accrued expenses and Other long-term liabilities on June 30, 2017 and within Prepaid expenses and other and Other long-term liabilities on December 31, 2016 in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

[3] These amounts relate to currency forward contracts valued primarily based on observable inputs, including forward and spot prices for currencies, net of contracted rates and then multiplied by notional amounts, and are included within Prepaid expenses and other and Accounts payable and accrued expenses on June 30, 2017 and December 31, 2016, in the consolidated balance sheet with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.