Employee Benefits - Schedule of Costs of Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net periodic benefit cost:
Interest cost	$ 45.7	$ 44.1
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (income):
Settlement adjustment	(1.8)	(10.9)	$ (7.6)
Other Postretirement Benefits Plan
Net periodic benefit cost:
Service cost		0.0	5.4
Interest cost	45.7	44.1	51.1
Expected return on plan assets	(57.3)	(60.0)	(59.3)
Amortization of prior net losses	12.8	14.6	15.5
Amortization of prior net service credit	(0.4)	(0.4)	0.0
Settlement adjustment	1.8	10.9	7.6
Net periodic pension cost	2.6	9.2	20.3
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (income):
Net actuarial gains (losses) and other adjustments	51.9	(0.9)	(43.7)
Net prior service credit		0.0	(10.7)
Settlement adjustment	(1.8)	(10.9)	(7.6)
Amortization of prior net losses	(12.8)	(14.6)	(15.5)
Amortization of prior net service credit	0.4	0.4	0.0
Total recognized in other comprehensive loss (income)	37.7	(26.0)	(77.5)
Total recognized in net periodic benefit cost and other comprehensive loss (income)	$ 40.3	$ (16.8)	$ (57.2)