Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	$ 26,300	$ 27,670	$ 26,001	$ 26,882
Other comprehensive income (loss) before reclassification adjustments, pretax	(68)	40	(220)	258
Tax	45	4	2	7
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(23)	44	(218)	265
Reclassification adjustments, pretax	27	(73)	28	(101)
Tax	(6)	13	(10)	19
Reclassification adjustments, net of taxes	21	(60)	18	(82)
Other comprehensive income (loss), net of taxes	(2)	(16)	(200)	183
Equity, ending balance	27,744	27,737	27,744	27,737
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	135	118	31	166
Other comprehensive income (loss) before reclassification adjustments, pretax	(110)	10	68	(3)
Tax	23	(2)	(14)	1
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(87)	8	54	(2)
Reclassification adjustments, pretax	(42)	(76)	(89)	(124)
Tax	9	16	19	26
Reclassification adjustments, net of taxes	(33)	(60)	(70)	(98)
Other comprehensive income (loss), net of taxes	(120)	(52)	(16)	(100)
Equity, ending balance	15	66	15	66
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	0	4	18	(78)
Other comprehensive income (loss) before reclassification adjustments, pretax	0	55	3	131
Tax	0	0	0	0
Other comprehensive income (loss) before reclassification adjustments, net of taxes	0	55	3	131
Reclassification adjustments, pretax	0	(11)	(21)	(5)
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	(11)	(21)	(5)
Other comprehensive income (loss), net of taxes	0	44	(18)	126
Equity, ending balance	0	48	0	48
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(4,201)	(3,541)	(4,261)	(3,556)
Other comprehensive income (loss) before reclassification adjustments, pretax	(21)	0	(21)	(1)
Tax	6	0	11	6
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(15)	0	(10)	5
Reclassification adjustments, pretax	69	14	138	28
Tax	(15)	(3)	(29)	(7)
Reclassification adjustments, net of taxes	54	11	109	21
Other comprehensive income (loss), net of taxes	39	11	99	26
Equity, ending balance	(4,162)	(3,530)	(4,162)	(3,530)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(2,325)	(1,927)	(1,981)	(2,077)
Other comprehensive income (loss) before reclassification adjustments, pretax	63	(25)	(270)	131
Tax	16	6	5	0
Other comprehensive income (loss) before reclassification adjustments, net of taxes	79	(19)	(265)	131
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	79	(19)	(265)	131
Equity, ending balance	(2,246)	(1,946)	(2,246)	(1,946)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(6,391)	(5,346)	(6,193)	(5,545)
Equity, ending balance	$ (6,393)	$ (5,362)	$ (6,393)	$ (5,362)