Note 4 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Reported Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		$ 36,978	$ 28,316
Fair Value, Net Asset (Liability), Total		34,733	25,421
Reported Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	99	102
Reported Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	928	362
Reported Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	(3,272)	(3,359)
Estimate of Fair Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		36,978	28,316
Fair Value, Net Asset (Liability), Total		34,733	25,421
Estimate of Fair Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	99	102
Estimate of Fair Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	928	362
Estimate of Fair Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	(3,272)	(3,359)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents (including restricted cash accounts)		36,978	28,316
Fair Value, Net Asset (Liability), Total		36,978	28,316
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents (including restricted cash accounts)		0	0
Fair Value, Net Asset (Liability), Total		928	362
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	928	362
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents (including restricted cash accounts)		0	0
Fair Value, Net Asset (Liability), Total		(3,173)	(3,257)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	99	102
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	$ (3,272)	$ (3,359)

[1] These amounts relate to contingent receivables and payables relating to acquisition of the Guadeloupe power plant, 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, 2020 and December 31, 2019 in the consolidated balance sheets with the corresponding gain or loss being recognized within "Derivatives and foreign currency transaction gains (losses)" in the condensed consolidated statements of operations and comprehensive income.

[2] 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", as applicable, on March 31, 2020 and December 31, 2019, in the condensed 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.