Income Taxes - Changes 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
Gross amounts of unrecognized tax benefits as of the beginning of the period	$ 551	$ 487	$ 458
Increases related to prior period tax positions	44	64	37
Decreases related to prior period tax positions	(114)	(10)	(28)
Increases related to current period tax positions	28	28	58
Settlements	(122)	(18)	(38)
Gross amounts of unrecognized tax benefits as of the end of the period	$ 387	$ 551	$ 487

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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