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Other Comprehensive Income (Loss) - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	$ 27,670	$ 33,901	$ 26,882	$ 34,569
Other comprehensive income (loss) before reclassification adjustments, pretax	40	(54)	258	(33)
Tax	4	(115)	7	(135)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	44	(169)	265	(168)
Reclassification adjustments, pretax	(73)	132	(101)	281
Tax	13	(25)	19	(51)
Reclassification adjustments, net of taxes	(60)	107	(82)	230
Other comprehensive income (loss), net of taxes	(16)	(62)	183	62
Adoption of ASU 2018-02				(266)
Adoption of ASU 2016-01					$ (8)
Equity, ending balance	27,737	32,766	27,737	32,766
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	118	(201)	166	(108)
Other comprehensive income (loss) before reclassification adjustments, pretax	10	265	(3)	84
Tax	(2)	(56)	1	(18)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	8	209	(2)	66
Reclassification adjustments, pretax	(76)	72	(124)	164
Tax	16	(15)	26	(34)
Reclassification adjustments, net of taxes	(60)	57	(98)	130
Other comprehensive income (loss), net of taxes	(52)	266	(100)	196
Adoption of ASU 2018-02				(23)
Adoption of ASU 2016-01					0
Equity, ending balance	66	65	66	65
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	4	(167)	(78)	(61)
Other comprehensive income (loss) before reclassification adjustments, pretax	55	(17)	131	(133)
Tax	0	0	0	1
Other comprehensive income (loss) before reclassification adjustments, net of taxes	55	(17)	131	(132)
Reclassification adjustments, pretax	(11)	20	(5)	36
Tax	0	0	0	0
Reclassification adjustments, net of taxes	(11)	20	(5)	36
Other comprehensive income (loss), net of taxes	44	3	126	(96)
Adoption of ASU 2018-02				1
Adoption of ASU 2016-01					(8)
Equity, ending balance	48	(164)	48	(164)
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(3,541)	(3,095)	(3,556)	(2,787)
Other comprehensive income (loss) before reclassification adjustments, pretax	0	(1)	(1)	(2)
Tax	0	1	6	4
Other comprehensive income (loss) before reclassification adjustments, net of taxes	0	0	5	2
Reclassification adjustments, pretax	14	40	28	81
Tax	(3)	(10)	(7)	(17)
Reclassification adjustments, net of taxes	11	30	21	64
Other comprehensive income (loss), net of taxes	11	30	26	66
Adoption of ASU 2018-02				(344)
Adoption of ASU 2016-01					0
Equity, ending balance	(3,530)	(3,065)	(3,530)	(3,065)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(1,927)	(1,597)	(2,077)	(1,954)
Other comprehensive income (loss) before reclassification adjustments, pretax	(25)	(301)	131	18
Tax	6	(60)	0	(122)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(19)	(361)	131	(104)
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	(19)	(361)	131	(104)
Adoption of ASU 2018-02				100
Adoption of ASU 2016-01					$ 0
Equity, ending balance	(1,946)	(1,958)	(1,946)	(1,958)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(5,346)	(5,060)	(5,545)	(4,910)
Equity, ending balance	$ (5,362)	$ (5,122)	$ (5,362)	$ (5,122)

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Tax Cuts and Jobs Act, Reclassification From AOCI to Retained Earnings, Tax Effect

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