Note 14 - Senior Notes - Carrying Amount of Senior Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying amount	$ 987,617	$ 986,597
Senior Notes 5.625% Due February 2020 [Member]
Carrying amount	248,595	247,853
Senior Notes 5.5% Due January 2024 [Member]
Carrying amount	248,736	248,585
Senior Notes 6% Due January 2043 [Member]
Carrying amount	$ 490,286	$ 490,159

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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Balance Type:	credit
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