Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Amortization of Net Loss [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	$ (2.6)	$ (6.1)	$ (16.7)	$ (17.9)
Amortization of Prior Service Credit [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	3.4	4.6	11.6	13.7
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	0.8	(1.5)	(5.1)	(4.2)
Income tax (expense) benefit	(0.1)	0.5	1.1	1.5
Total reclassifications for the period, net of income taxes	$ 0.7	$ (1.0)	$ (4.0)	$ (2.7)