Note 2 - Divestiture (Details) (USD $)	1 Months Ended		6 Months Ended	12 Months Ended
	Dec. 31, 2012	Apr. 27, 2012	Jun. 30, 2013	Dec. 31, 2012
Note 2 - Divestiture (Details) [Line Items]
Ownership Percentage Sold	49.00%	49.00%		49.00%
Capital And Exploratory Expenditures Funding Agreement		$ 185,000,000	$ 112,000,000	$ 126,300,000
Participating Interest Loans		65,000,000
Transaction Costs				5,700,000
Gain (Loss) on Disposition of Oil and Gas Property	26,900,000
Gain Loss On Sale Of Oil And Gas Property Net Of Tax	31,100,000
Sale Adjustments Prior To Closing	18,300,000			18,300,000
Other Liabilities, Current	21,792,000		21,556,000	21,792,000
Other Liabilities, Noncurrent	20,755,000		20,755,000	20,755,000
Collection Of Revenue [Member]
Note 2 - Divestiture (Details) [Line Items]
Sale Adjustments Prior To Closing	56,100,000			56,100,000
Payment Of Expenses [Member]
Note 2 - Divestiture (Details) [Line Items]
Sale Adjustments Prior To Closing	32,600,000			32,600,000
Income Taxes [Member]
Note 2 - Divestiture (Details) [Line Items]
Sale Adjustments Prior To Closing	5,200,000			5,200,000
Gross Sales Price [Member]
Note 2 - Divestiture (Details) [Line Items]
Proceeds from Sale of Oil and Gas Property and Equipment		150,000,000
Block Z-1 [Member]
Note 2 - Divestiture (Details) [Line Items]
Proceeds from Sale of Oil and Gas Property and Equipment		85,000,000
Ownership Percentage Sold	49.00%		49.00%	49.00%
Other Liabilities, Current			19,900,000
Other Liabilities, Noncurrent			$ 20,800,000