Retirement Benefits (Details 5) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 1,894.6	$ 1,962.3
Actual returns on plan assets and plan expenses	304.1	79.7
Employer contributions	143.4	125.1
Participant contributions	0.0	0.2
Effect of currency rates	7.6	(17.3)
Benefits paid	220.1	255.4
Fair value of plan assets at end of year	2,129.6	1,894.6
Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.7	1.8
Actual returns on plan assets and plan expenses	0.2	(0.8)
Employer contributions	0.0	0.0
Participant contributions	0.0	0.0
Effect of currency rates	0.0	0.0
Benefits paid	0.3	0.3
Fair value of plan assets at end of year	$ 0.6	$ 0.7