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Basis Of Presentation Derivative Instruments (Details) - Interest Rate Swap - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative [Line Items]
Derivative, Notional Amount	$ 1,000		$ 1,000
Not Designated as Hedging Instrument \| Interest expense
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	$ 0	(8)	$ 59
Not Designated as Hedging Instrument \| Other non-current liabilities
Derivative [Line Items]
Interest rate swap contract - other current and non-current liabilities	57		57		$ 81
November 2017
Derivative [Line Items]
Derivative, Notional Amount	450		450
August 2020
Derivative [Line Items]
Derivative, Notional Amount	400		400
November 2022
Derivative [Line Items]
Derivative, Notional Amount	$ 150		$ 150