Retirement Benefits - Schedule of Changes in Projected Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year	$ 49.9	$ 57.8	$ 48.3
Service cost	1.7	1.8	1.6
Interest cost	2.1	2.0	2.0
Actuarial (gain) loss	8.8	(5.6)	3.7
Benefits paid	(2.6)	(2.0)	(1.4)
Cumulative translation adjustments	2.2	(4.1)	3.6
Benefit obligation, end of year	$ 62.1	$ 49.9	$ 57.8