Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Amortization of Net Loss [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	$ (5.9)	$ (5.1)	$ (11.8)	$ (10.2)
Amortization of Prior Service Credit [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	4.6	1.2	9.1	2.5
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	(1.3)	(3.9)	(2.7)	(7.7)
Income tax benefit	0.5	1.4	1.0	2.7
Total reclassifications for the period, net of income taxes	$ (0.8)	$ (2.5)	$ (1.7)	$ (5.0)