Retirement Benefits Plans (Cumulative Amounts Not Yet Recognized in Net Income) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan
Cumulative amounts not yet recognized in net income (loss):
Actuarial losses	$ 0.0	$ 13.5
Prior service costs (benefits)	0.0	0.5
Accumulated other comprehensive loss (before related tax benefit)	0.0	14.0
Postretirement Benefit Plans
Cumulative amounts not yet recognized in net income (loss):
Actuarial losses	10.6	10.0
Prior service costs (benefits)	(3.1)	(8.4)
Accumulated other comprehensive loss (before related tax benefit)	$ 7.5	$ 1.6