Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Lease obligations		$ 72.8	$ 77.0
Employee benefits and compensation		44.8	44.0
Accrued liabilities		30.4	28.9
Net operating loss carryforwards		16.2	19.8
Inventories		13.4	7.9
Pension and postretirement benefits		12.7	30.4
Restricted stock and performance units		9.8	8.7
Capital loss and general business credit carryforwards		0.4	0.5
Derivatives		0.1	0.1
Gross deferred tax assets		200.6	217.3
Valuation allowance	[1]	(0.3)	(0.4)
Net deferred tax assets		200.3	216.9
Deferred tax liabilities:
Property, plant and equipment		(609.2)	(609.0)
Goodwill and intangible assets		(79.0)	(75.9)
Right-of-use assets		(70.1)	(75.0)
Total deferred tax liabilities		(758.3)	(759.9)
Net deferred tax liabilities		$ (558.0)	$ (543.0)

[1] Deferred tax assets are reduced by a valuation allowance when it is more likely than not that some portion of the deferred tax assets will not be realized. Both the 2023 and 2022 valuation allowances relate to capital losses. We do not expect to generate capital gains before the capital losses expire. If or when recognized, the tax benefits relating to the reversal of any or all of the valuation allowance would be recognized as a benefit to income tax expense.