Income Taxes - Reconciliation of unrecognized tax benefits (UTB) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal, State and Foreign Tax
Gross UTB Balance at January 1	$ 647	$ 530	$ 319
Additions based on tax positions related to the current year	76	129	119
Additions for tax positions of prior years	132	146	149
Additions related to recent acquisitions	396
Reductions for tax positions of prior years	(56)	(123)	(38)
Settlements (UTB decreases)	(4)	(17)	(3)
Reductions due to lapse of applicable statute of limitations	(24)	(18)	(16)
Gross UTB Balance at December 31	$ 1,167	$ 647	$ 530

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 settlements with taxing authorities.

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