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Basis Of Presentation Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Foreign Exchange Contract
Derivative [Line Items]
Derivative, Notional Amount	$ 33		$ 33		$ 27
Foreign Exchange Contract \| Not Designated as Hedging Instrument \| Operating expense
Derivative [Line Items]
Location of (Gain) or Loss Recognized for Derivative Instruments	1	$ 0	1	$ 1
Foreign Exchange Contract \| Maximum
Derivative [Line Items]
Fair value of derivative instrument	1		1		1
Interest Rate Swap \| Not Designated as Hedging Instrument \| Interest expense
Derivative [Line Items]
Location of (Gain) or Loss Recognized for Derivative Instruments	12	$ (7)	50	$ (19)
Interest Rate Swap \| Not Designated as Hedging Instrument \| Other non-current assets
Derivative [Line Items]
Interest rate swap contract - other non-current assets	0		0		6
Interest Rate Swap \| Not Designated as Hedging Instrument \| Other current and non-current liabilities
Derivative [Line Items]
Interest rate swap contract - other current and non-current liabilities	60		60		$ 16
Interest Rate Swap \| August 2015
Derivative [Line Items]
Derivative, Notional Amount	600		600
Interest Rate Swap \| November 2017
Derivative [Line Items]
Derivative, Notional Amount	450		450
Interest Rate Swap \| August 2020
Derivative [Line Items]
Derivative, Notional Amount	400		400
Interest Rate Swap \| November 2022
Derivative [Line Items]
Derivative, Notional Amount	$ 150		$ 150