Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net loss	$ (616.2)	$ (545.7)	$ (540.8)
Other comprehensive (loss) income, net of tax:
Pension, SERP and Retiree medical adjustments, net of tax	70.8	(121.4)	136.3
Unrealized foreign exchange gain (loss) on intercompany loan, net of effect	1.8	(4.4)	(0.4)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	9.8	(23.7)	(2.0)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(0.5)	18.7	0.8
Foreign currency translation adjustments	32.4	(49.4)	(4.3)
Total other comprehensive income (loss), net of tax	114.3	(180.2)	130.4
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest		0.5	0.0
Total comprehensive loss	$ (501.9)	$ (725.9)	$ (410.4)