Note 2 - Investments (Details Textual) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Equity Securities, FV-NI	$ 17.4		$ 6.2
Equity Securities, FV-NI, Cost	11.3		$ 9.8
Equity Securities, FV-NI, Unrealized Gain (Loss), Total	9.4	$ (1.2)
Available-for-sale Equity Securities, Acquired During Period, Cost Basis	$ 1.7	0.4
Available-for-sale Equity Securities, Sold During Period, Cost Basis		0.9
Proceeds from Sale of Available-for-sale Securities, Equity		1.8
Equity Securities, FV-NI, Realized Gain (Loss), Total		$ 0.9