Employee Benefit Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5.4	$ 5.9
Interest cost	7.4	10.0
Expected return on plan assets	(15.8)	(14.2)
Net amortization of unrecognized amounts, Prior service cost	1.0	1.1
Net amortization of unrecognized amounts, Actuarial loss (income)	2.5	2.7
Net periodic benefit cost	$ 0.5	$ 5.5