Note 20 - Incentive Plans - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options outstanding (in shares)	3,464,946	6,013,729	9,012,441
Options outstanding, weighted average exercise price per share (in dollars per share)	$ 18.78	$ 27.81	$ 32.09	$ 31.09
Options outstanding, aggregate intrinsic value	$ 0.4		$ 12.1	$ 27.4
Options exercised, shares (in shares)	(42,259)	(83,863)	(1,167,819)
Options exercised, weighted average exercise price per share (in dollars per share)	$ 14	$ 18.20	$ 18.03
Options exercised, aggregate intrinsic value	$ 0.1	$ 3.4	$ 12.4
Options forfeited, shares (in shares)	(1,781,321)	(2,464,920)	(1,830,893)
Options forfeited, weighted average exercise price per share (in dollars per share)	$ 36.53	$ 35.91	$ 39.69
Options outstanding (in shares)	1,641,366	3,464,946	6,013,729
Options exercisable (fully vested) -
Options Exercisable, Shares (in shares)	1,641,366	3,464,946	5,144,416
Options exercisable, weighted average exercise price per share (in dollars per share)	$ 18.78	$ 27.81	$ 32.56
Options exercisable, aggregate intrinsic value	$ 0.4	$ 4.0	$ 11.3