Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	$ 27,744	$ 27,737	$ 26,001	$ 26,882
Other comprehensive income (loss) before reclassification adjustments, pretax	(143)	106	(362)	364
Tax	77	(72)	79	(65)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(66)	34	(283)	299
Reclassification adjustments, pretax	94	(75)	121	(176)
Tax	(18)	13	(28)	32
Reclassification adjustments, net of taxes	76	(62)	93	(144)
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Equity, ending balance	29,270	26,925	29,270	26,925
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	15	66	31	166
Other comprehensive income (loss) before reclassification adjustments, pretax	(195)	186	(126)	183
Tax	41	(39)	27	(38)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(154)	147	(99)	145
Reclassification adjustments, pretax	22	(71)	(68)	(195)
Tax	(5)	15	14	41
Reclassification adjustments, net of taxes	17	(56)	(54)	(154)
Other comprehensive income (loss), net of taxes	(137)	91	(153)	(9)
Equity, ending balance	(122)	157	(122)	157
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	0	48	18	(78)
Other comprehensive income (loss) before reclassification adjustments, pretax	0	8	3	139
Tax	0	0	0	0
Other comprehensive income (loss) before reclassification adjustments, net of taxes	0	8	3	139
Reclassification adjustments, pretax	0	(25)	(21)	(30)
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	(25)	(21)	(30)
Other comprehensive income (loss), net of taxes	0	(17)	(18)	109
Equity, ending balance	0	31	0	31
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(4,162)	(3,530)	(4,261)	(3,556)
Other comprehensive income (loss) before reclassification adjustments, pretax	2	(4)	(19)	(5)
Tax	1	0	12	6
Other comprehensive income (loss) before reclassification adjustments, net of taxes	3	(4)	(7)	1
Reclassification adjustments, pretax	72	21	210	49
Tax	(13)	(2)	(42)	(9)
Reclassification adjustments, net of taxes	59	19	168	40
Other comprehensive income (loss), net of taxes	62	15	161	41
Equity, ending balance	(4,100)	(3,515)	(4,100)	(3,515)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(2,246)	(1,946)	(1,981)	(2,077)
Other comprehensive income (loss) before reclassification adjustments, pretax	50	(84)	(220)	47
Tax	35	(33)	40	(33)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	85	(117)	(180)	14
Reclassification adjustments, pretax	0	0	0	0
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	0	0	0
Other comprehensive income (loss), net of taxes	85	(117)	(180)	14
Equity, ending balance	(2,161)	(2,063)	(2,161)	(2,063)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(6,393)	(5,362)	(6,193)	(5,545)
Equity, ending balance	$ (6,383)	$ (5,390)	$ (6,383)	$ (5,390)