Income Taxes (Summary of Activity Related to 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]
Beginning Balance	$ 4,652	$ 4,696	$ 5,393
Increases related to prior year tax positions	938	321	685
Decreases related to prior year tax positions	(143)	(623)	(257)
Decreases related to settlement with tax authorities	(2,886)	(191)	(1,875)
Increases related to current year tax positions	816	449	750
Ending Balance	$ 3,377	$ 4,652	$ 4,696

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

No definition available.

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- Definition

Amount of unrecognized tax benefits.

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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 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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