Income Taxes (Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Income Tax Contingency [Line Items]
Income tax (expense) benefit	$ (10)	$ (108)
Effective Income Tax Rate, Continuing Operations	5.00%	(22.00%)
Income Tax Uncertainties [Abstract]
Unrecognized Tax Benefits	$ 28
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	16
Unrecognized Tax Benefit Related to Deferred Tax Asset	12
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	2
Minimum [Member]
Income Tax Contingency [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	0
Maximum [Member]
Income Tax Contingency [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 8

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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 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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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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