Employee Benefit Plans - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Curtailment loss (gain)	$ 9.8	$ 0.0	$ 3.2
Settlement charge	9.8	0.0	0.0
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1.5	2.6	3.6
Interest cost	28.0	27.3	28.9
Expected asset return	(41.1)	(45.8)	(44.0)
Amortized actuarial loss	6.4	7.8	7.1
Amortized prior service cost (credit)	0.0	0.1	(0.1)
Curtailment loss (gain)	0.0	3.2	0.0
Settlement charge	10.4	0.4	3.2
Net periodic benefit cost (credit)	5.2	(4.4)	(1.3)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.3	0.4	0.3
Interest cost	12.8	12.4	13.3
Expected asset return	0.0	0.0	0.0
Amortized actuarial loss	0.1	0.8	0.6
Amortized prior service cost (credit)	(1.5)	(2.7)	(2.7)
Curtailment loss (gain)	0.0	(0.6)	0.0
Settlement charge	0.0	0.0	0.0
Other postretirement benefit expense	$ 11.7	$ 10.3	$ 11.5