Note 3 - Long-term Debt - Long-term Debt Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long-term debt including current portion:
Senior Credit Facility	$ 1,860,234
Total outstanding principal	1,860,234	$ 1,781,438
Less current portion	(6,417)	0
Net carrying value	1,831,011	1,756,747
Borrowing availability under the Revolving Credit Facility	100,000	60,000
2014 Senior Credit Facility [Member]
Long-term debt including current portion:
Senior Credit Facility	0	556,438
Unamortized deferred loan costs	0	(12,158)
The 2017 Senior Credit Facility [Member]
Long-term debt including current portion:
Senior Credit Facility	635,234	0
Unamortized deferred loan costs	(11,777)	0
2024 Notes [Member]
Long-term debt including current portion:
Senior Credit Facility	525,000
Unsecured Debt	525,000	525,000
Unamortized deferred loan costs	(6,743)	(7,742)
2026 Notes [Member]
Long-term debt including current portion:
Senior Credit Facility	700,000
Unsecured Debt	700,000	700,000
Unamortized deferred loan costs	(9,473)	(10,588)
Unamortized premium	$ 5,187	$ 5,797

Total Long term debt including current portion and before unamortized premium or discount.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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