Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate (as a percent)	23.00%	23.80%	21.70%	22.70%
Unrecognized tax benefits	$ 114		$ 114		$ 147
Accrued interest and penalties associated with unrecognized tax benefits	20		20		$ 35
Reduction of unrecognized tax benefits is reasonably possible	$ 5		$ 5

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of unrecognized tax benefits.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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