Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Benefits
Components of net periodic benefit cost
Service cost	$ 0.1	$ 0.1	$ 0.0
Interest cost	0.8	1.0	0.4
Recognition/establishment of Germany benefit obligation	0.0	0.0	0.0
Expected return on plan assets	0.0	0.0	0.0
Defined Benefit Plan, Other Cost (Credit)	0.0	0.0	0.0
Amortization of prior service cost	0.0	0.0	0.0
Recognized net actuarial loss	0.4	0.4	0.0
Settlement loss	0.0	0.0	0.0
Net periodic pension benefit cost	1.3	1.5	0.4
Prior service credit/loss recognized during the year	0.0	0.0
U.S. Plans | Pension Benefits
Components of net periodic benefit cost
Service cost	3.8	3.7	3.9
Interest cost	18.9	22.1	20.6
Recognition/establishment of Germany benefit obligation	0.0	0.0	0.0
Expected return on plan assets	(25.4)	(24.7)	(24.6)
Defined Benefit Plan, Other Cost (Credit)	0.0	0.0	0.0
Amortization of prior service cost	0.0	0.0	0.0
Recognized net actuarial loss	7.8	5.1	6.6
Settlement loss	0.0	0.0	0.0
Net periodic pension benefit cost	5.1	6.2	6.5
Prior service credit/loss recognized during the year	0.0	0.0
Foreign Plan [Member] | Pension Benefits
Components of net periodic benefit cost
Service cost	9.8	9.8	11.0
Interest cost	4.0	6.5	6.2
Recognition/establishment of Germany benefit obligation	0.0	7.1	0.0
Expected return on plan assets	(13.4)	(12.3)	(10.5)
Defined Benefit Plan, Other Cost (Credit)	0.2	0.0	0.0
Amortization of prior service cost	2.8	(0.1)	0.0
Recognized net actuarial loss	(0.6)	(1.5)	(0.7)
Settlement loss	1.1	(0.9)	(2.2)
Net periodic pension benefit cost	3.9	8.6	$ 3.8
Prior service credit/loss recognized during the year	$ 0.7	$ (0.5)