Retirement Benefit Plans - Change in Benefit Obligation (Details) - Pension Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 11.5	$ 15.0
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	8.1	7.4	$ 9.1
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	2.8	0.0
Defined Benefit Plan, Fair Value of Plan Assets	531.9	529.6	553.7
Change in benefit obligation:
Benefit obligation at beginning of year	612.4	589.9
Service cost	12.2	13.1	15.4
Interest cost	24.6	26.6	45.6
Amendments	2.8	0.0
Actuarial losses	60.5	45.3
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)	0.0	0.0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	(1.8)	0.0
Defined Benefit Plan, Plan Assets, Benefits Paid	67.7	62.5
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0.0	0.0	0.0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement			(1,100.0)
Benefit obligation at end of year	643.0	612.4	589.9
Actual return on plan assets	65.5	33.8
Defined Benefit Plan, Plan Assets, Contributions by Employer	4.5	4.6
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	0.0	0.0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(111.1)	(82.8)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Reclassification Adjustment, before Tax	(1.4)	(1.7)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	(0.7)	0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0.0	0.0	(116.1)
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	0.5	0.5	0.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	0.0	0.0
Defined Benefit Plan, Fair Value of Plan Assets	292.4	268.7	304.6
Change in benefit obligation:
Benefit obligation at beginning of year	314.2	338.1
Service cost	1.6	1.4	2.2
Interest cost	7.5	10.5	12.3
Amendments	0.0	0.0
Actuarial losses	0.9	53.4
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)	32.2	(45.0)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	0.0	(0.1)
Defined Benefit Plan, Plan Assets, Benefits Paid	21.2	44.1
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0.0	0.0	0.6
Benefit obligation at end of year	335.2	314.2	338.1
Actual return on plan assets	12.0	43.2
Defined Benefit Plan, Plan Assets, Contributions by Employer	7.0	10.4
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	25.9	(45.4)
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(42.8)	(45.5)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Reclassification Adjustment, before Tax	0.0	(0.1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	0.0	0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 0.0	$ 0.0	$ 0.0