Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
Jan. 01, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 4,589		$ 4,589		$ 4,589
Adoption of new accounting guidance related to reclassification of certain tax effects	(45)	$ 0	(45)		(45)
Ending balance		3,788			3,788
AOCI
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ (1,287)	(1,240)	(1,287)	$ (1,643)	(1,287)	$ (1,807)
Ending balance		(1,530)	$ (1,240)	(1,516)	(1,530)	(1,516)
Accumulated Foreign Currency Translation Adjustment
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), adjustments during the period		(270)		60	(201)	204
Income taxes		(29)		57	(15)	67
Other comprehensive income (loss), net of tax		(299)		117	(216)	271
Accumulated Pension and Other Postretirement Benefit Adjustments
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), adjustments during the period		0		0	1	0
Other comprehensive income (loss), adjustments reclassified to income		11		13	21	27
Income taxes		(2)		(3)	(4)	(7)
Other comprehensive income (loss), net of tax		$ 9		$ 10	$ 18	$ 20

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

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Amount before tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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