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Income Taxes - Reconciliation of Change in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gross Unrecognized Tax Benefits
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 440	$ 86	$ 85
Additions for tax positions related to the current year	23	28
Additions for tax positions related to prior years	12	402	5
Reductions for tax positions related to prior years due to IRS and other settlements	(44)	(76)	(4)
Ending balance	431	440	86
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	164
Accrued Interest and Penalties
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	35	29	24
Additions for tax positions related to the current year	17	0
Additions for tax positions related to prior years	4	25	7
Reductions for tax positions related to prior years due to IRS and other settlements	(25)	(19)	(2)
Ending balance	31	35	29
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	24
Gross Tax, Interest and Penalties
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	475	115	109
Additions for tax positions related to the current year	40	28
Additions for tax positions related to prior years	16	427	12
Reductions for tax positions related to prior years due to IRS and other settlements	(69)	(95)	(6)
Ending balance	462	$ 475	$ 115
Portion of balance at December 31, that, if recognized, would impact the effective income tax rate	$ 188

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Amount of unrecognized tax benefits.

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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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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 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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