Income Taxes (Summary Of Significant Components Of Deferred Income Tax Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract]
Net operating loss carryforwards	$ 3,308.9	$ 3,028.7
Property and equipment	1,535.1	1,454.8
Interest limitation carryforwards	123.4	193.4
Employee benefits, including share-based compensation	41.6	43.1
Foreign tax credits	44.7	60.7
Premiums on long-term debt	6.0	8.1
Other	14.4	20.1
Valuation allowance	(4,192.4)	(4,720.3)
Total deferred tax assets	881.7	88.6
Deferred tax liabilities	26.8	19.4
Deferred Tax Assets, Net	$ 854.9	$ 69.2

Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Deferred Tax Assets Premium On Long Term Debt

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