Pensions and Other Postretirement Benefits - Pension and Postretirement Expenses (Details) - Pension Benefit Plans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Components of Net Periodic Cost:
Service Cost	$ 3.0	$ 4.0	$ 8.0	$ 8.0
Interest Cost	2.0	4.0	4.0	7.0
Expected Return on Plan Assets	(4.0)	(5.0)	(9.0)	(12.0)
Net Settlement Loss	0.0	0.0	0.0	153.0
Amortization:
Actuarial Loss	1.0	1.0	2.0	3.0
Net Periodic Cost	$ 2.0	$ 4.0	$ 5.0	$ 159.0