Post Retirement Benefit Plans - Changes in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in benefit obligation:
Benefit obligation at beginning of year	$ 255.0	$ 216.7
Service cost	8.2	6.4	$ 7.5
Interest cost	1.1	2.6	2.0
Plan participant contributions	4.4	4.8
Plan amendments	(2.8)
Benefits paid	(5.7)	(2.8)
Actuarial loss (gain)	(6.7)	25.8
Premiums paid	1.4	1.6
Impact of foreign currency exchange rates	23.1	3.1
Benefit obligation at end of year	275.2	255.0	216.7
Change in plan assets:
Fair value of plan assets at beginning of year	131.4	124.6
Return on plan assets	3.1	(2.5)
Plan participant and employer contributions	10.7	11.6
Benefits paid	(5.7)	(2.8)
Premiums paid	(1.5)	(1.7)
Impact of foreign currency exchange rates	12.5	2.2
Fair value of plan assets at end of year	150.5	131.4	124.6
Net under funded status	(124.7)	(123.6)
Interest and other income (expense), net	(22.5)	(20.5)	$ (17.7)
Accumulated benefit obligation	$ 260.4	$ 243.6