Employee Benefit Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6.2	$ 6.2
Interest cost	11.7	10.6
Expected return on plan assets	(13.0)	(14.2)
Net amortization of unrecognized amounts, Prior service cost	1.6	1.8
Net amortization of unrecognized amounts, Actuarial loss (income)	1.7	2.3
Net periodic benefit cost	$ 8.2	$ 6.7