Note I - Long-Term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Note I - Long-Term Debt (Details) [Line Items]
Credit Facility Syndication Number Of Commercial Banks	11
Line Of Credit Facility Stated Borrowing Period	5 years
Line of Credit Facility, Expiration Date	Mar. 14, 2017
Line Of Credit Facility, Maximum Borrowing Capacity Without Borrowing Base Requirement	$ 400,000,000
Line Of Credit Facility, Accordion Feature, Additional Revolving Credit Commitments Under Existing Loan Facility	100,000,000
Debt Issuance Cost		2,000,000
Long-term Debt, Excluding Current Maturities	40,000,000	105,000,000
Line of Credit Facility, Remaining Borrowing Capacity	357,000,000
Line of Credit Facility, Current Borrowing Capacity	314,000,000
Deferred Finance Costs, Net	4,600,000	4,600,000
Accumulated Amortization, Deferred Finance Costs	3,100,000	2,600,000
Amortization of Financing Costs	476,000	562,000	499,000
Letters of Credit Outstanding, Amount	3,000,000	2,900,000
Amended Agreement [Member]
Note I - Long-Term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500,000,000
Previous Agreement [Member]
Note I - Long-Term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 350,000,000
Minimum [Member]
Note I - Long-Term Debt (Details) [Line Items]
Line Of Credit Facility, Fixed Charge Coverage Ratio, Covenant	1.25
Line of Credit Facility, Interest Rate During Period	1.42%
Maximum [Member]
Note I - Long-Term Debt (Details) [Line Items]
Line Of Credit Facility, Leverage Ratio Covenant	3.75
Line of Credit Facility, Interest Rate During Period	1.46%