Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Sep. 30, 2016		Dec. 31, 2015
Reported Value Measurement [Member] | Forward Contracts [Member]
Assets:
Derivative assets		$ 249	[1]	$ 7
Derivative liabilities		(30)		(169)
Liabilities:
Derivative liabilities		30		169
Derivative liabilities		(30)		(169)
Reported Value Measurement [Member] | Call and Put Options on Oil Price [Member]
Assets:
Derivative liabilities	[1]	1,776
Liabilities:
Derivative liabilities	[1]	(1,776)
Derivative liabilities	[1]	1,776
Reported Value Measurement [Member] | Call Option on Natural Gas Price [Member]
Assets:
Derivative liabilities		1,534
Liabilities:
Derivative liabilities		(1,534)
Derivative liabilities		1,534
Reported Value Measurement [Member]
Assets:
Cash equivalents (including restricted cash accounts)		12,635		31,428
		9,544		31,266
Liabilities:
		9,544		31,266
Fair Value, Inputs, Level 1 [Member] | Forward Contracts [Member]
Assets:
Derivative assets			[1]
Derivative liabilities			[1]
Liabilities:
Derivative liabilities			[1]
Derivative liabilities			[1]
Fair Value, Inputs, Level 1 [Member] | Call and Put Options on Oil Price [Member]
Assets:
Derivative liabilities	[2]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 1 [Member] | Call Option on Natural Gas Price [Member]
Assets:
Derivative liabilities	[2]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents (including restricted cash accounts)		12,635		31,428
		12,635		31,428
Liabilities:
		12,635		31,428
Fair Value, Inputs, Level 2 [Member] | Forward Contracts [Member]
Assets:
Derivative assets		249	[1]	7
Derivative liabilities		(30)	[1]	(169)
Liabilities:
Derivative liabilities		30	[1]	169
Derivative liabilities		(30)	[1]	(169)
Fair Value, Inputs, Level 2 [Member] | Call and Put Options on Oil Price [Member]
Assets:
Derivative liabilities	[2]	1,776
Liabilities:
Derivative liabilities	[2]	(1,776)
Derivative liabilities	[2]	1,776
Fair Value, Inputs, Level 2 [Member] | Call Option on Natural Gas Price [Member]
Assets:
Derivative liabilities	[2]	1,534
Liabilities:
Derivative liabilities	[2]	(1,534)
Derivative liabilities	[2]	1,534
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents (including restricted cash accounts)
		(3,091)		(162)
Liabilities:
		(3,091)		(162)
Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member]
Assets:
Derivative assets			[1]
Derivative liabilities			[1]
Liabilities:
Derivative liabilities			[1]
Derivative liabilities			[1]
Fair Value, Inputs, Level 3 [Member] | Call and Put Options on Oil Price [Member]
Assets:
Derivative liabilities	[2]
Liabilities:
Derivative liabilities	[2]
Derivative liabilities	[2]
Fair Value, Inputs, Level 3 [Member] | Call Option on Natural Gas Price [Member]
Assets:
Derivative liabilities	[2]
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		249	[1]	7
Derivative liabilities		(30)	[1]	(169)
Liabilities:
Derivative liabilities		30	[1]	169
Derivative liabilities		(30)	[1]	(169)
Call and Put Options on Oil Price [Member]
Assets:
Derivative liabilities	[2]	1,776
Liabilities:
Derivative liabilities	[2]	(1,776)
Derivative liabilities	[2]	1,776
Call Option on Natural Gas Price [Member]
Assets:
Derivative liabilities	[2]	1,534
Liabilities:
Derivative liabilities	[2]	(1,534)
Derivative liabilities	[2]	1,534
Cash equivalents (including restricted cash accounts)		90,066		185,919
Cash equivalents (including restricted cash accounts)		12,635		31,428
		9,544		31,266
		$ 9,544		$ 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 September 30, 2016 and December 31, 2015, in the consolidated balance sheet with the corresponding gain or loss being recognized within "Derivatives and foreign 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 September 30, 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.