Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Lease obligations		$ 77.0	$ 61.4
Employee benefits and compensation		44.0	44.7
Pension and postretirement benefits		30.4	33.8
Accrued liabilities		28.9	6.3
Net operating loss carryforwards		19.8	23.4
Restricted stock and performance units		8.7	8.5
Inventories		7.9	6.8
Capital loss and general business credit carryforwards		0.5	0.7
Derivatives		0.1	0.1
Gross deferred tax assets		217.3	185.7
Valuation allowance	[1]	(0.4)	(0.6)
Net deferred tax assets		216.9	185.1
Deferred tax liabilities:
Property, plant and equipment		(609.0)	(518.0)
Goodwill and intangible assets		(75.9)	(73.3)
Right-of-use assets		(75.0)	(59.7)
Total deferred tax liabilities		(759.9)	(651.0)
Net deferred tax liabilities		$ (543.0)	$ (465.9)

[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 2022 and 2021 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.