Note 5- Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended			6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Amended Agreement [Member]	Mar. 13, 2012 Previous Agreement [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]
Note 5- Long-Term Debt (Details) [Line Items]
Credit Facility Syndication Number Of Commercial Banks	11
Line of Credit Facility, Maximum Borrowing Capacity		$ 500.0	$ 350.0
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	400.0
Line Of Credit Facility, Accordion Feature, Additional Revolving Credit Commitments Under Existing Loan Facility	100.0
Debt Issuance Cost	2.0
Line Of Credit Facility, Fixed Charge Coverage Ratio, Covenant				1.00	1.25
Line Of Credit Facility, Leverage Ratio Covenant				1.00	3.75
Line of Credit Facility, Interest Rate During Period				1.45%	1.46%
Long-term Debt	75.0
Letters of Credit Outstanding, Amount	3.0
Line of Credit Facility, Remaining Borrowing Capacity	322.0
Line of Credit Facility, Current Borrowing Capacity	$ 290.6