Postretirement and Other Benefits - Net Pension Benefit Costs (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0.0	$ 0.0	$ 0.0
Interest cost	3.7	4.6	4.3
Expected return on plan assets	(4.9)	(5.8)	(5.8)
Amortizations and other	3.3	2.0	3.2
Net periodic benefit cost	2.1	0.8	1.7
France
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1.3	1.0	1.1
Interest cost	0.2	0.4	0.4
Expected return on plan assets	(0.1)	(0.1)	(0.1)
Amortizations and other	1.0	0.9	1.1
Net periodic benefit cost	$ 2.4	$ 2.2	$ 2.5