Other Comprehensive Earnings/Losses (Changes in Each Component of Accumulated Other Comprehensive Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ 12,770
Other comprehensive earnings (losses) before reclassifications	$ 522	$ (72)	226	$ (207)
Other comprehensive deferred income taxes	(182)	25	(78)	83
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	340	(47)	148	(124)
Amounts reclassified to net earnings	54	56	108	104
Amounts reclassified to net earnings, deferred income taxes	(20)	(22)	(42)	(40)
Amounts reclassified to net earnings, net of deferred income taxes	34	34	66	64
Other comprehensive earnings (losses), net of deferred income taxes	374	(13)	214	(60)	$ 1,228
Ending balance	12,418		12,418		12,770
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(4)	(4)	(4)	(5)	(5)
Other comprehensive earnings (losses) before reclassifications	1	0	1	1
Other comprehensive deferred income taxes	0	0	0	0
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	1	0	1	1
Amounts reclassified to net earnings	0	0	0	0
Amounts reclassified to net earnings, deferred income taxes	0	0	0	0
Amounts reclassified to net earnings, net of deferred income taxes	0	0	0	0
Other comprehensive earnings (losses), net of deferred income taxes	1	0	1	1
Ending balance	(3)	(4)	(3)	(4)	(4)
Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,016)	(2,184)	(2,048)	(2,010)	(2,010)
Other comprehensive earnings (losses) before reclassifications	0	0	0	(318)
Other comprehensive deferred income taxes	0	0	0	122
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	0	0	0	(196)
Amounts reclassified to net earnings	52	49	106	85
Amounts reclassified to net earnings, deferred income taxes	(19)	(19)	(41)	(33)
Amounts reclassified to net earnings, net of deferred income taxes	33	30	65	52
Other comprehensive earnings (losses), net of deferred income taxes	33	30	65	(144)
Ending balance	(1,983)	(2,154)	(1,983)	(2,154)	(2,048)
Accumulated Equity Method Investments Attributable to Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(192)	(1,139)	0	(1,265)	(1,265)
Other comprehensive earnings (losses) before reclassifications	521	(72)	225	110
Other comprehensive deferred income taxes	(182)	25	(78)	(39)
Other comprehensive earnings (losses) before reclassifications, net of deferred income taxes	339	(47)	147	71
Amounts reclassified to net earnings	2	7	2	19
Amounts reclassified to net earnings, deferred income taxes	(1)	(3)	(1)	(7)
Amounts reclassified to net earnings, net of deferred income taxes	1	4	1	12
Other comprehensive earnings (losses), net of deferred income taxes	340	(43)	148	83
Ending balance	148	(1,182)	148	(1,182)	0
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,212)	(3,327)	(2,052)	(3,280)	(3,280)
Other comprehensive earnings (losses), net of deferred income taxes			214		1,228
Ending balance	$ (1,838)	$ (3,340)	$ (1,838)	$ (3,340)	$ (2,052)