Postretirement Benefits Other Than Pensions - Components Of Comprehensive OPEB (Income) Expense (Details) - Other Postretirement Benefit Plan, Defined Benefit - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service Cost Earned During the Year	$ 0.2	$ 0.3	$ 0.2
Interest Cost on Accumulated Postretirement Benefit Obligation	0.2	0.1	0.3
Amortization of Prior Service Credit	(1.3)	(1.3)	(1.3)
Amortization of Accumulated Unrecognized OPEB Gain	(1.8)	(1.7)	(1.9)
Pension Expense Recognized in Consolidated Statements of (Loss) Income	(2.7)	(2.6)	(2.7)
Unrecognized OPEB (Gain) Loss Arising During the Year	(2.5)	(1.8)	1.9
Prior Service Credit Arising During the Year from Plan Amendments				$ 11.0
Prior Service Cost Arising During the Year	1.3	1.3	1.3
Amortization of Accumulated Unrecognized OPEB Gain	1.8	1.7	1.9
Comprehensive OPEB (Income) Expense	$ (2.1)	$ (1.4)	$ 2.4