Note 3 - Long-term Debt Summary (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
2014 Senior Credit Facility [Member]
Long-term debt including current portion:
Long-term Debt, Gross	$ 556,438,000	$ 556,438,000
2020 Notes [Member]
Long-term debt including current portion:
Long-term Debt, Gross	675,000,000
Unsecured Debt	675,000,000	675,000,000
Unamortized net premium - 2020 Notes	4,099,000	4,963,000
2014 Revolving Credit Facility [Member]
Long-term debt including current portion:
Long-term Debt, Gross	556,400,000
Line of Credit Facility, Remaining Borrowing Capacity	50,000,000	50,000,000
Long-term Debt, Gross	1,231,438,000
Total outstanding principal	1,231,438,000	1,231,438,000
Net carrying value	$ 1,235,537,000	$ 1,236,401,000