Note 14 - Senior Notes - Carrying Amount of Senior Notes (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Carrying amount	$ 1,036,900,000	$ 989,422,000
Senior Notes 5.625% Due February 2020 [Member]
Carrying amount	0	249,909,000
Senior Notes 5.5% Due January 2024 [Member]
Carrying amount	249,060,000	249,005,000
Senior Notes, 3 Point 85 Percent, Due January 2030 [Member]
Carrying amount	297,285,000	0
Senior Notes 6% Due January 2043 [Member]
Carrying amount	$ 490,555	$ 490,508

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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