Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax (Changes in AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (350)	$ (504)	$ (489)
Other Comprehensive Income (Loss) before Reclassifications	(230)	143	(11)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	30	11	(4)
Net Current Period Other Comprehensive Income (Loss)	(200)	154	(15)
Ending Balance	(550)	(350)	(504)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6)	(9)	(15)
Other Comprehensive Income (Loss) before Reclassifications	0	0	(4)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	3	3	10
Net Current Period Other Comprehensive Income (Loss)	3	3	6
Ending Balance	(3)	(6)	(9)
Pension and OPEB Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(355)	(545)	(499)
Other Comprehensive Income (Loss) before Reclassifications	(72)	176	(58)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	1	14	12
Net Current Period Other Comprehensive Income (Loss)	(71)	190	(46)
Ending Balance	(426)	(355)	(545)
Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	11	50	25
Other Comprehensive Income (Loss) before Reclassifications	(158)	(33)	51
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	26	(6)	(26)
Net Current Period Other Comprehensive Income (Loss)	(132)	(39)	25
Ending Balance	$ (121)	$ 11	$ 50