Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			$ 9,260
Other comprehensive income (loss), net of tax	$ 44	$ 265	(43)	$ (527)
Balance, end of period	10,264	8,392	10,264	8,392
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(5,197)	(5,847)	(5,110)	(5,055)
Other comprehensive income (loss), before reclassification, net of tax	8	234	(119)	(587)
Amounts reclassified from accumulated other comprehensive income	36	31	76	60
Other comprehensive income (loss), net of tax	44	265	(43)	(527)
Balance, end of period	(5,153)	(5,582)	(5,153)	(5,582)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(4,122)	(3,374)	(4,126)	(3,512)
Other comprehensive income (loss), before reclassification, net of tax	(16)	(3)	(52)	106
Amounts reclassified from accumulated other comprehensive income	36	31	76	60
Other comprehensive income (loss), net of tax	20	28	24	166
Balance, end of period	(4,102)	(3,346)	(4,102)	(3,346)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(1,075)	(2,473)	(984)	(1,543)
Other comprehensive income (loss), before reclassification, net of tax	24	237	(67)	(693)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive income (loss), net of tax	24	237	(67)	(693)
Balance, end of period	$ (1,051)	$ (2,236)	$ (1,051)	$ (2,236)