Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 11,392	$ 9,462
Cumulative impact from adoption of new revenue accounting standard			$ 3
Other comprehensive income (loss) before reclassifications	9	(24)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	(10)	10
Ending balance	11,596	9,819
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(629)	(623)
Cumulative impact from adoption of new revenue accounting standard			3
Other comprehensive income (loss) before reclassifications	2	1
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	0	0
Ending balance	(627)	(619)
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	23
Other comprehensive income (loss) before reclassifications	13
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	(11)
Ending balance	25
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(15)
Cumulative impact from adoption of new revenue accounting standard			0
Other comprehensive income (loss) before reclassifications		(22)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings		10
Ending balance		(27)
Unrealized gain (loss) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	5	0
Cumulative impact from adoption of new revenue accounting standard			$ 0
Other comprehensive income (loss) before reclassifications	(6)	(3)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	1	0
Ending balance	0	(3)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(601)	(638)
Ending balance	$ (602)	$ (649)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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