Retirement Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined benefit plan, cost recognized	$ 73.1	$ 58.6	$ 58.4
Other postretirement benefits payable	26.2	23.1
Retirement Plans [Member]
Prior service cost/(credit)	3.9	$ 3.7
Estimated amounts of contributions expected to be paid to the plans in next fiscal year	$ 24.5