Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Amount of expense (income) related to adjustment to fair value of warrant liability.

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Derivative Instruments (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Number of securities called by each warrant or right					84.5
Exercise price of warrants or rights					$ 6.43
Warrants and rights outstanding	$ 0
Fair Value Adjustment of Warrants	0	$ (46)
Foreign currency forward contracts
Derivative [Line Items]
Notional amount	519			$ 435
Other, Net \| Not Designated as Hedging Instrument \| Foreign currency forward contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	5	$ 1
Capital in Excess of Par Value
Derivative [Line Items]
Stock issued during period, shares, new issues			84.5
Other Current Liabilities [Member] \| Not Designated as Hedging Instrument \| Foreign currency forward contracts
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 1