Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Reported Value Measurement [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]	$ 38	$ 7
Liabilities:
Derivative liabilities	[1]	(190)	(169)
Derivative liabilities	[1]	190	169
Reported Value Measurement [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]	(2,349)
Derivative liabilities	[2]	2,349
Reported Value Measurement [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities		(2,779)
Derivative liabilities		2,779
Reported Value Measurement [Member]
Assets:
Cash equivalents (including restricted cash accounts)		23,965	31,428
Liabilities:
		19,065	31,266
Fair Value, Inputs, Level 1 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]
Liabilities:
Derivative liabilities	[1]
Derivative liabilities	[1]
Fair Value, Inputs, Level 1 [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 1 [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents (including restricted cash accounts)		23,965	31,428
Liabilities:
		23,965	31,428
		(23,965)	(31,428)
Fair Value, Inputs, Level 2 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]	38	7
Liabilities:
Derivative liabilities	[1]	(190)	(169)
Derivative liabilities	[1]	190	169
Fair Value, Inputs, Level 2 [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]	(2,349)
Derivative liabilities	[2]	2,349
Fair Value, Inputs, Level 2 [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]	(2,779)
Derivative liabilities	[2]	2,779
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents (including restricted cash accounts)
Liabilities:
		4,900	162
		(4,900)	(162)
Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]
Liabilities:
Derivative liabilities	[1]
Derivative liabilities	[1]
Fair Value, Inputs, Level 3 [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 3 [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash equivalents (including restricted cash accounts)
Liabilities:
Forward Contracts [Member]
Assets:
Derivative assets	[1]	38	7
Liabilities:
Derivative liabilities	[1]	(190)	169
Derivative liabilities	[1]	190	(169)
Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]	(2,349)
Derivative liabilities	[2]	2,349
Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]	(2,779)
Derivative liabilities	[2]	2,779
Cash equivalents (including restricted cash accounts)		192,556	185,919
Cash equivalents (including restricted cash accounts)		23,965	31,428
		19,065	31,266
		$ (19,065)	$ (31,266)

[1] These amounts relate to derivatives which represent 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 June 30, 2016 and December 31, 2015, in the consolidated balance sheet with the corresponding gain or loss being recognized within “Foreign currency translation and transaction gains (losses)” in the consolidated statement of operations and comprehensive income.

[2] These amounts relate to call and put option transactions on oil and natural gas prices, valued primarily based on observable inputs, including spot prices for related commodity indices, and is included within “Accounts payable and accrued expenses” on June 30, 2016 in the consolidated balance sheets with the corresponding gain or loss being recognized within “Foreign currency translation and transaction losses” in the consolidated statement of operations and comprehensive income.