Pensions and Other Postretirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefit Plans
Components of Net Periodic Cost:
Service Cost	$ 14.0	$ 17.3	$ 8.2
Interest Cost	46.1	41.8	42.6
Expected Return on Plan Assets	(54.9)	(63.6)	(64.1)
Amortization:
Prior Service Cost (Credit)	0.2	0.4	0.5
Actuarial Loss (Gain)	10.0	5.9	6.5
Net Curtailment/Settlement Loss	39.2	1.0	0.0
Other	0.3	0.5	0.8
Net Periodic Cost (Benefit)	54.9	3.3	(5.5)
Posretirement Benefits
Components of Net Periodic Cost:
Service Cost	0.5	0.6	0.8
Interest Cost	1.2	1.2	1.3
Expected Return on Plan Assets	0.0	0.0	0.0
Amortization:
Prior Service Cost (Credit)	(0.3)	(0.3)	(0.3)
Actuarial Loss (Gain)	(2.3)	(1.8)	(2.1)
Net Curtailment/Settlement Loss	0.0	0.0	0.0
Other	0.0	0.0	0.0
Net Periodic Cost (Benefit)	$ (0.9)	$ (0.3)	$ (0.3)