Accumulated Other Comprehensive Income (Loss) - Components of the Company's AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, deferred taxes	$ (416)	$ (95)	$ (39)
Balance	6,896	5,029	5,960
Change in value, deferred tax	38	(321)	(53)
Change in value	(130)	1,118	184
Amounts reclassified to earnings, deferred taxes	31	0	(3)
Amounts reclassified to earnings	(107)	(1)	13
Balance, deferred taxes	(347)	(416)	(95)
Balance	9,324	6,896	5,029
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	175	(942)	(1,139)
Balance	(62)	175	(942)
Deferred income taxes	285
Pension and Other Postretirement Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	626	(847)	(1,102)
Change in value, before tax	(199)	1,474	239
Amounts reclassified to earnings, before tax	(138)	(1)	16
Balance, before tax	289	626	(847)
Investments and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	(35)	0	2
Change in value, before tax	31	(35)	(2)
Amounts reclassified to earnings, before tax	0	0	0
Balance, before tax	$ (4)	$ (35)	$ 0