Note 4 - Fair Value Measurements - Summary of Activities in Financial Instruments With Level 3 Inputs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Balance	$ 16.1	$ 19.0	$ 14.2	$ 18.8
Fair value change included in net loss	0.7	0.6	2.6	0.8
Balance	16.8	19.6	16.8	19.6
Changes in unrealized gains or losses for the period included in earnings (or changes in net assets) for liabilities held at the end of the reporting period	$ 0.7	$ 0.6	$ 2.6	$ 0.8