Note 21 - Incentive Plans - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options outstanding (in shares)	1,297,936	1,641,366	3,464,946
Options outstanding, weighted average exercise price per share (in dollars per share)	$ 20.03	$ 19.60	$ 18.78	$ 27.81
Options outstanding, aggregate intrinsic value	$ 0.0	$ 2.0	$ 0.4	$ 0.0
Options exercised, shares (in shares)	(63,365)	(268,856)	(42,259)
Options exercised, weighted average exercise price per share (in dollars per share)	$ 15.48	$ 14.43	$ 14.00
Options exercised, aggregate intrinsic value	$ 0.2	$ 1.1	$ 0.1
Options forfeited, shares (in shares)	(72,250)	(74,574)	(1,781,321)
Options forfeited, weighted average exercise price per share (in dollars per share)	$ 16.20	$ 20.24	$ 36.53
Options outstanding (in shares)	1,162,321	1,297,936	1,641,366
Options Exercisable, Shares (in shares)	1,162,321	1,297,936	1,641,366
Options exercisable, weighted average exercise price per share (in dollars per share)	$ 20.03	$ 19.60	$ 18.78
Options exercisable, aggregate intrinsic value	$ 0.0	$ 2.0	$ 0.4