Accumulated Other Comprehensive Income (Loss) - Components of the Company's AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, deferred taxes	$ (39)	$ (160)	$ (136)
Balance	5,960	11,531	10,042
Change in value, deferred tax	(53)	221	(24)
Change in value	184	(772)	88
Amounts reclassified to earnings, deferred taxes	(3)	(100)	0
Amounts reclassified to earnings	13	351	(3)
Balance, deferred taxes	(95)	(39)	(160)
Balance	5,029	5,960	11,531
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(1,139)	(718)	(803)
Balance	(942)	(1,139)	(718)
Deferred income tax expense	285
Pension and Other Postretirement Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	(1,102)	(560)	(663)
Change in value, before tax	239	(993)	105
Amounts reclassified to earnings, before tax	16	451	(2)
Balance, before tax	(847)	(1,102)	(560)
Investments and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	2	2	(4)
Change in value, before tax	(2)	0	7
Amounts reclassified to earnings, before tax	0	0	(1)
Balance, before tax	$ 0	$ 2	$ 2