Retirement Benefits Plans (Defined Benefit Plan Expense (Benefit) Components) (Details) - Defined Benefit Plan - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined benefit plan expense (benefit)
Interest cost on benefit obligations		$ 0.7	$ 1.5	$ 1.3
Expected return on plan assets		(0.7)	(1.8)	(2.4)
Settlement loss	$ 12.6	12.6	0.0	0.0
Amortization of:
Actuarial losses		0.5	0.5	1.0
Benefit plan (benefit) expense, total		$ 13.1	$ 0.2	$ (0.1)