Pension and Other Postretirement Benefit Plans - Reconciliation of Net Postretirement Health and Life Amounts Recognized in Consolidated Balance Sheet (Details) - Postretirement Health and Life [Member] - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net Loss	[1]	$ (16.0)	$ (25.0)
Prior Service Credit		36.3	4.6
Accumulated Net Periodic Benefit Cost in Excess of Contributions		3.6	(1.3)
Total Net Postretirement Health and Life Amounts Recognized in Consolidated Balance Sheet		$ 23.9	$ (21.7)

[1] Excludes gains, losses and contributions associated with irrevocable grantor trusts.