Note 7 - Long-Term Debt (Details) (USD $)	3 Months Ended			6 Months Ended			6 Months Ended
	Jun. 30, 2014	May 16, 2014	Dec. 31, 2013	Jun. 30, 2014 Previous Agreement [Member]	Jun. 30, 2014 Amended Agreement [Member]	May 16, 2014 Letter of Credit [Member]	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 Maximum [Member]
Note 7 - Long-Term Debt (Details) [Line Items]
Credit Facility Syndication Number Of Commercial Banks		11
Line of Credit Facility, Maximum Borrowing Capacity		$ 500,000,000				$ 30,000,000
Line of Credit Facility, Expiration Date				Mar. 14, 2017	May 16, 2019
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	800,000
Line Of Credit Facility, Fixed Charge Coverage Ratio, Covenant							1.25
Line Of Credit Facility, Leverage Ratio Covenant								3.75
Line of Credit Facility, Interest Rate During Period							1.40%	3.25%
Long-term Debt, Excluding Current Maturities	132,808,000		40,000,000
Letters of Credit Outstanding, Amount	1,800,000
Line of Credit Facility, Remaining Borrowing Capacity	265,400,000
Line of Credit Facility, Current Borrowing Capacity	$ 260,100,000