Note 3 - Long-term Debt (Details Textual) - USD ($) $ in Thousands				1 Months Ended	12 Months Ended
	Feb. 07, 2017	Sep. 14, 2016	Feb. 16, 2016	Sep. 30, 2016	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Jun. 14, 2016
Long-term Debt, Gross					$ 1,781,438
Proceeds from Issuance of Long-term Debt					1,656,000		$ 0	$ 644,000
Gain (Loss) on Extinguishment of Debt					(31,987)			(5,086)
Interest Paid					76,200		76,900	61,900
Interest Costs Capitalized					0		0	$ 0
The 2017 Senior Credit Facility [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 100,000
The 2017 Senior Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Subsequent Event [Member]
Debt Instrument, Basis Spread on Variable Rate	2.50%
2014 Senior Credit Facility [Member]
Long-term Debt, Gross					$ 556,438	[1]	$ 556,438
Debt Instrument, Interest Rate, Stated Percentage					3.90%		3.80%
2014 Senior Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 60,000
Line of Credit Facility, Increase			10,000
2016 Term Loan [Member]
Long-term Debt, Gross			$ 425,000
2026 Notes [Member]
Long-term Debt, Gross					$ 700,000
Debt Instrument, Interest Rate, Stated Percentage					5.875%
Debt Instrument, Face Amount									$ 500,000
Unsecured Debt					$ 700,000
Debt Instrument, Redemption Price, Percentage					100.00%
Debt Instrument, Redemption Price, Net Proceeds from Equity Offerings, Percentage					35.00%
The Additional 2026 Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage					5.875%
Debt Instrument, Face Amount		$ 200,000
Debt Instrument, Issueing Price, Percentage		103.00%
Proceeds from Issuance of Long-term Debt		$ 206,000
Debt Instrument, Interest Rate, Effective Percentage					5.398%
2024 Notes [Member]
Long-term Debt, Gross					$ 525,000
Debt Instrument, Interest Rate, Stated Percentage					5.125%
Debt Instrument, Face Amount		$ 525,000
Unsecured Debt					$ 525,000
Debt Instrument, Redemption Price, Percentage					100.00%
Debt Instrument, Redemption Price, Net Proceeds from Equity Offerings, Percentage					35.00%
2020 Notes [Member]
Debt Instrument, Face Amount				$ 431,200
Unsecured Debt							$ 675,000
Debt Instrument, Redemption Price, Percentage				103.75%
Gain (Loss) on Extinguishment of Debt					(32,000)
Extinguishment of Debt, Gain (Loss), Net of Tax					(19,500)
Payments of Tender Offer Premiums					18,200
Payments for Debt Instrument, Debt Extinguishment, Call Premium					9,100
Write off of Deferred Debt Issuance Cost					8,000
Payments of Debt Extinguishment Costs					200
Un-accredited Net Premium, Recognized					$ 3,500

[1] Pursuant to the 2017 Senior Credit Facility, the maturity date of the term loan was extended to February 7, 2024.