Tax Matters - Reconciliation of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, beginning	$ (6,259)	$ (6,558)	$ (5,826)
Acquisitions	(44)	0
Acquisitions			10
Increases based on tax positions taken during a prior period	(36)	(192)	(49)
Decreases based on tax positions taken during a prior period	1,109	561	28
Decreases based on settlements for a prior period	100	123	35
Increases based on tax positions taken during the current period	(383)	(370)	(753)
Impact of foreign exchange	25	56	(121)
Other, net	107	121	118
Balance, ending	$ (5,381)	$ (6,259)	$ (6,558)

Unrecognized Tax Benefits, Increase (Decrease) Resulting from Foreign Currency Translation

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Unrecognized Tax Benefits, Period Increase (Decrease), Other

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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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- Definition

Amount of unrecognized tax benefits.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Amount of decrease in unrecognized tax benefits resulting from acquisitions.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from acquisitions.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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