Accumulated Other Comprehensive Income (Loss) (Components of Other Accumulated Comprehensive Income Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 9,260	$ 7,943
Other comprehensive gain (loss) before reclassifications	376	(180)
Amounts reclassified from accumulated other comprehensive loss	159	125
Other comprehensive income (loss), net of tax	535	(55)	$ (408)
Ending balance	11,222	9,260	7,943
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(5,110)	(5,055)	(4,647)
Other comprehensive income (loss), net of tax	535	(55)	(408)
Ending balance	(4,575)	(5,110)	(5,055)
Pension and Post-Retirement Plans Losses
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(4,126)	(3,512)
Other comprehensive gain (loss) before reclassifications	765	(739)
Amounts reclassified from accumulated other comprehensive loss	159	125	84
Other comprehensive income (loss), net of tax	924	(614)	(559)
Ending balance	(3,202)	(4,126)	(3,512)
Foreign Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(984)	(1,543)
Other comprehensive gain (loss) before reclassifications	(389)	559	151
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive income (loss), net of tax	(389)	559
Ending balance	$ (1,373)	$ (984)	$ (1,543)