Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 24,737	$ 22,270
Other comprehensive income (loss) before reclassifications		269	(75)
Reclassification of certain tax effects		(84)
Amounts reclassified into (out of) earnings		(9)	10
Other comprehensive income (loss)		176	(65)
Ending balance		25,038	22,350
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(1,356)	(1,009)
Reclassification of certain tax effects	[1]	(84)
Ending balance		(1,180)	(1,074)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(89)	(56)
Other comprehensive income (loss) before reclassifications		24	(97)
Reclassification of certain tax effects		(6)
Amounts reclassified into (out of) earnings		0	0
Other comprehensive income (loss)		18	(97)
Ending balance		(71)	(153)
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(175)	103
Other comprehensive income (loss) before reclassifications		270	(130)
Reclassification of certain tax effects		21
Amounts reclassified into (out of) earnings		0	(1)
Other comprehensive income (loss)		291	(131)
Ending balance		116	(28)
Net Unrealized Losses on Hedges of Net Investments in Non-U.S. Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		16	(65)
Other comprehensive income (loss) before reclassifications		23	(36)
Reclassification of certain tax effects		(3)
Amounts reclassified into (out of) earnings		0	0
Other comprehensive income (loss)		20	(36)
Ending balance		36	(101)
Other-Than-Temporary Impairment on Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(2)	(6)
Other comprehensive income (loss) before reclassifications		1	1
Reclassification of certain tax effects		(1)
Amounts reclassified into (out of) earnings		(1)	(1)
Other comprehensive income (loss)		(1)	0
Ending balance		(3)	(6)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(143)	(170)
Other comprehensive income (loss) before reclassifications		0	0
Reclassification of certain tax effects		(28)
Amounts reclassified into (out of) earnings		(8)	12
Other comprehensive income (loss)		(36)	12
Ending balance		(179)	(158)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(963)	(815)
Other comprehensive income (loss) before reclassifications		(49)	187
Reclassification of certain tax effects		(67)
Amounts reclassified into (out of) earnings		0	0
Other comprehensive income (loss)		(116)	187
Ending balance		$ (1,079)	$ (628)

[1] ⁽¹⁾ Represents the reclassification from accumulated other comprehensive income into retained earnings as a result of our adoption of ASU 2018-02 - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income in the first quarter of 2019.