Note 16 - Lines of Credit and Total Debt Obligations - Carrying Amount of Senior Notes (Details) (Parentheticals) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Oct. 16, 2017
Senior Notes 5.625% Due February 2020 [Member]
Senior Notes, interest rate	5.625%	5.625%
Senior notes, maturity date	Feb. 28, 2020	Feb. 28, 2020
Senior Notes, face amount	$ 250.0	$ 250.0
Senior Notes 5.5% Due January 2024 [Member]
Senior Notes, interest rate	5.50%	5.50%
Senior notes, maturity date	Jan. 31, 2024	Jan. 31, 2024
Senior Notes, face amount	$ 250.0	$ 250.0
Senior Notes 6% Due January 2043 [Member]
Senior Notes, interest rate	6.00%	6.00%
Senior notes, maturity date	Jan. 31, 2043	Jan. 31, 2043
Senior Notes, face amount	$ 500.0	$ 500.0	$ 500.0

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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-Name Accounting Standards Codification
-Topic 210
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