Income Taxes (Components of Deferred Tax Balances) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax liabilities:
Differences between book and tax basis of property	$ 255	$ 379
Derivative activity	137	0
Right of use lease asset	34	41
Accrued pension costs	0	1
Other	3	3
Total deferred tax liabilities	429	424
Deferred tax assets:
Accrued compensation	53	50
Accrued pension costs	1	0
Asset retirement obligations	27	24
Net operating loss carryforward	450	469
Future lease payments	35	41
Derivative activity	0	340
Capital loss carryover	26	27
Interest carryover	93	41
Research and development credits	17	0
Other	17	21
Total deferred tax assets	719	1,013
Valuation allowance	(52)	(589)	$ (1,079)
Net deferred tax asset	$ 238	$ 0