Other Post-Employment Benefits and Other Employee Benefit Plans - Reconciliation of Benefit Obligations, Plan Assets and Funded Status for Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in plan assets:
Fair value of plan assets at beginning of period	$ 762.0
Fair value of plan assets at end of period	836.6	$ 762.0
Other Post-Employment Benefits and Other Employee Benefit Plans
Change in benefit obligations:
Benefit obligation at beginning of period	43.5	46.4
Interest cost	1.0	1.6	$ 1.4
Actuarial loss	2.4	(1.2)
Benefits paid, net	(3.5)	(3.3)
Benefit obligation at end of period	43.4	43.5	46.4
Change in plan assets:
Fair value of plan assets at beginning of period	0.0	0.0
Employer contribution	3.5	3.3
Benefits paid, net	(3.5)	(3.3)
Fair value of plan assets at end of period	0.0	0.0	$ 0.0
Net amount recognized:
Underfunded status at end of year	(43.4)	(43.5)
Accumulated benefit obligation at end of year	43.4	43.5
Net amount recognized in consolidated balance sheets consists of:
Current liability	(5.1)	(5.3)
Non-current liability	(38.3)	(38.2)
Net amount recognized	(43.4)	(43.5)
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial loss (gain)	1.9	(0.6)
Prior service credit	(2.3)	(2.6)
Total	$ (0.4)	$ (3.2)