Note 3 - Financing Arrangements - Outstanding Borrowings (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Senior Notes [Member]
Long-term Debt, Total	$ 1,305.4	$ 1,295.7

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant