Other Comprehensive Earnings/Losses (Changes in Each Component of Accumulated Other Comprehensive Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 14,789	$ 15,380	$ 12,773
Adoption of ASU No. 2018-02				$ (397)
Other comprehensive earnings (losses), net of deferred income taxes	(317)	(242)	155
Ending balances	6,319	14,789	15,380
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,547)	(1,897)	(2,052)
Adoption of ASU No. 2018-02				(408)
Other comprehensive earnings (losses) before reclassifications	(545)	(475)	(39)
Deferred income taxes	126	103	11
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	(419)	(372)	(28)
Amounts reclassified to net earnings (losses)	139	177	299
Deferred income taxes	(37)	(47)	(116)
Amounts reclassified to net earnings (losses), net of deferred income taxes	102	130	183
Other comprehensive earnings (losses), net of deferred income taxes	(317)	(242)	155
Ending balances	(2,864)	(2,547)	(1,897)
Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,168)	(1,839)	(2,048)
Other comprehensive earnings (losses) before reclassifications	(204)	(151)	52
Deferred income taxes	51	39	(21)
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	(153)	(112)	31
Amounts reclassified to net earnings (losses)	173	241	291
Deferred income taxes	(44)	(61)	(113)
Amounts reclassified to net earnings (losses), net of deferred income taxes	129	180	178
Other comprehensive earnings (losses), net of deferred income taxes	(24)	68	209
Ending balances	(2,192)	(2,168)	(1,839)
Accumulated Equity Method Investments Attributable To Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(374)	(54)	0
Other comprehensive earnings (losses) before reclassifications	(367)	(323)	(91)
Deferred income taxes	75	64	32
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	(292)	(259)	(59)
Amounts reclassified to net earnings (losses)	(34)	(64)	8
Deferred income taxes	7	14	(3)
Amounts reclassified to net earnings (losses), net of deferred income taxes	(27)	(50)	5
Other comprehensive earnings (losses), net of deferred income taxes	(319)	(309)	(54)
Ending balances	(693)	(374)	(54)
Currency Translation Adjustments and Other [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(5)	(4)	(4)
Other comprehensive earnings (losses) before reclassifications	26	(1)	0
Deferred income taxes	0	0	0
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	26	(1)	0
Amounts reclassified to net earnings (losses)	0	0	0
Deferred income taxes	0	0	0
Amounts reclassified to net earnings (losses), net of deferred income taxes	0	0	0
Other comprehensive earnings (losses), net of deferred income taxes	26	(1)	0
Ending balances	$ 21	$ (5)	$ (4)
Accounting Standards Update 2018-02 [Member] | Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Adoption of ASU No. 2018-02				(397)
Accounting Standards Update 2018-02 [Member] | Accumulated Equity Method Investments Attributable To Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Adoption of ASU No. 2018-02				(11)
Accounting Standards Update 2018-02 [Member] | Currency Translation Adjustments and Other [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Adoption of ASU No. 2018-02				$ 0