Note 6 - Pension and Other Postretirement Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plan [Member]
Service cost	$ 0.4	$ 0.4	$ 1.1	$ 1.3
Interest cost	3.4	3.6	10.3	11.0
Expected return on plan assets	$ (4.8)	$ (4.9)	$ (14.3)	(14.8)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)				0.1
Amortization of net actuarial losses	$ 1.2	$ 0.8	$ 3.4	2.1
Settlements			0.3	0.2
Net periodic cost	$ 0.2	$ (0.1)	$ 0.8	$ (0.1)
Other Postretirement Benefit Plan [Member]
Service cost
Interest cost		$ 0.1	$ 0.2	$ 0.3
Expected return on plan assets
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	$ (0.4)		$ (0.4)
Amortization of net actuarial losses	$ (0.1)	$ (0.1)	$ (0.8)
Settlements				$ (0.1)
Net periodic cost	$ (0.5)		$ (1.0)	$ 0.2