Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		$ 19,276	$ 14,922
Derivative Asset, Current	[1]	298
		(5,606)	874
Reported Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,472	1,443
Reported Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(24,662)	(11,581)
Reported Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[2]	(3,507)	(3,429)
Reported Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[3]	1,517
Derivative Liability, Current	[3]		(481)
Estimate of Fair Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		19,276	14,922
Derivative Asset, Current	[1]	298
		(5,606)	874
Estimate of Fair Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,472	1,443
Estimate of Fair Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(24,662)	(11,581)
Estimate of Fair Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[2]	(3,507)	(3,429)
Estimate of Fair Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[3]	1,517
Derivative Liability, Current	[3]		(481)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents (including restricted cash accounts)		19,276	14,922
Derivative Asset, Current	[1]
		19,276	14,922
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] | Warrant [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[3]
Derivative Liability, Current	[3]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents (including restricted cash accounts)
Derivative Asset, Current	[1]	298
		1,815	(481)
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] | Warrant [Member]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[3]	1,517
Derivative Liability, Current	[3]		(481)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents (including restricted cash accounts)
Derivative Asset, Current	[1]
		(26,697)	(13,567)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[2]	1,472	1,443
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[2]	(24,662)	(11,581)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Derivative Liability, Current	[2]	(3,507)	(3,429)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[3]
Derivative Liability, Current	[3]

[1] These amounts relate to put option transactions on natural gas prices, valued primarily based on observable inputs, including spot prices for related commodity indices, and are included within "Prepaid expenses and other" on March 31, 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 pertaining to the Viridity and Guadeloupe power plant purchase transactions, 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 March 31,2017 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, netted against contracted rates and then multiplied against notional amounts, and are included within "prepaid expenses and other" and "accounts payable and accrued expenses" on March 31, 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.