Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Reported Value Measurement [Member] | Forward Contracts [Member]
Assets:
Derivative assets		$ 1,759	$ 7
Liabilities:
Derivative liabilities			(169)
Reported Value Measurement [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities		(1,612)
Reported Value Measurement [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities		(1,196)
Reported Value Measurement [Member]
Assets:
Cash and cash equivalents		47,457	31,428
Liabilities:
		$ 46,408	$ 31,266
Fair Value, Inputs, Level 1 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]
Liabilities:
Derivative liabilities	[1]
Derivative liabilities	[1]
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]
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]
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents (including restricted cash accounts)		$ 47,457	$ 31,428
Liabilities:
		47,457	31,428
		(47,457)	(31,428)
Fair Value, Inputs, Level 2 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]	1,759	7
Liabilities:
Derivative liabilities	[1]		(169)
Derivative liabilities	[1]		169
Derivative liabilities	[1]		(169)
Derivative liabilities	[1]		$ 169
Fair Value, Inputs, Level 2 [Member] | Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]	(1,612)
Derivative liabilities	[2]	1,612
Derivative liabilities	[2]	(1,612)
Derivative liabilities	[2]	1,612
Fair Value, Inputs, Level 2 [Member] | Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]	(1,196)
Derivative liabilities	[2]	1,196
Derivative liabilities	[2]	(1,196)
Derivative liabilities	[2]	$ 1,196
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents (including restricted cash accounts)
Liabilities:
		$ 1,049	$ (162)
		$ (1,049)	$ 162
Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member]
Assets:
Derivative assets	[1]
Liabilities:
Derivative liabilities	[1]
Derivative liabilities	[1]
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]
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]
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]	$ 1,759	$ 7
Liabilities:
Derivative liabilities	[1]		169
Derivative liabilities	[1]		(169)
Derivative liabilities	[1]		169
Derivative liabilities	[1]		(169)
Call and Put Options on Oil Price [Member]
Liabilities:
Derivative liabilities	[2]	(1,612)
Derivative liabilities	[2]	1,612
Derivative liabilities	[2]	(1,612)
Derivative liabilities	[2]	1,612
Call Option on Natural Gas Price [Member]
Liabilities:
Derivative liabilities	[2]	(1,196)
Derivative liabilities	[2]	1,196
Derivative liabilities	[2]	(1,196)
Derivative liabilities	[2]	1,196
Cash and cash equivalents		148,498	185,919
Cash equivalents (including restricted cash accounts)		47,457	31,428
		46,408	31,266
		$ (46,408)	$ (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 "accounts payable and accrued expenses" on March 31, 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 March 31, 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.