Accumulated Other Comprehensive Income (Loss), Net of Tax (Changes of AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (522)	$ (410)	$ (550)	$ (350)	$ (350)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	(53)	18	(118)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	7	8	17	13
Other Comprehensive Income (Loss), net of tax	7	(45)	35	(105)
Accumulated Other Comprehensive Income (Loss), Ending Balance	(515)	(455)	(515)	(455)	(550)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(4)	(5)	(3)	(6)	(6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	12	0	10	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(1)	0	0	1	(3)
Other Comprehensive Income (Loss), net of tax	11	0	10	1
Accumulated Other Comprehensive Income (Loss), Ending Balance	7	(5)	7	(5)	(3)
Pension and OPEB Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(423)	(355)	(426)	(355)	(355)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0	0	0
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	4	1	7	1
Other Comprehensive Income (Loss), net of tax	4	1	7	1
Accumulated Other Comprehensive Income (Loss), Ending Balance	(419)	(354)	(419)	(354)	(426)
Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(95)	(50)	(121)	11	11
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(12)	(53)	8	(118)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	4	7	10	11
Other Comprehensive Income (Loss), net of tax	(8)	(46)	18	(107)
Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (103)	$ (96)	$ (103)	$ (96)	$ (121)