Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Effective tax rate	(20.00%)	3.00%	0.00%
Valuation allowance, deferred tax asset, amount	$ 512,000,000
Deferred income tax expense (benefit), tax provision recorded, before offset of release of valuation allowance	269,000,000
Effective income tax rate reconciliation, change in deferred tax assets valuation allowance, amount	526,000,000	$ 392,000,000	$ (2,000,000)
Change in deferred tax assets valuation allowance, reclassified from OCI, amount	14,000,000
Operating loss carryforward valuation allowance	52,000,000
Unrecognized tax benefits that would impact effective tax rate	0
Statutory depletion carryforward
Income Taxes [Line Items]
Tax credit carryforward	13,000,000
Interest deduction carryforward
Income Taxes [Line Items]
Tax credit carryforward	415,000,000
Exploration Program in Canada
Income Taxes [Line Items]
Net operating loss carryforward	29,000,000
Indigo Merger
Income Taxes [Line Items]
Operating loss carryforwards subject to a section 382 limitation	48,000,000
Other
Income Taxes [Line Items]
Operating loss carryforwards subject to a section 382 limitation	1,700,000
Net operating loss carryforward	856,000,000
Federal
Income Taxes [Line Items]
Income taxes paid	12,000,000	36,000,000	0
Operating loss carryforwards subject to a section 382 limitation	2,000,000,000
Net operating loss carryforward	4,000,000,000
Operating loss carryforwards, subject to expiration	3,000,000,000
Operating loss carryforwards, not subject to expiration	1,000,000,000
Statel
Income Taxes [Line Items]
Income taxes paid	$ 1,000,000	$ 5,000,000	$ 0