Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Accrued postretirement benefits cost	$ 8.4	$ 12.4
Accrued pension cost	46.5	49.9
Other employee benefit accruals	16.1	15.7
Tax loss and credit carryforwards	80.7	83.2
Other, net	61.7	63.9
Valuation allowances	(31.3)	(31.0)
Total deferred tax assets	182.1	194.1
Deferred tax liabilities - principally depreciation and amortization	(250.9)	(247.9)
Net deferred tax liabilities	$ (68.8)	$ (53.8)