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Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
Derivative Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 07, 2020
Interest rate swap contracts
Derivative [Line Items]
Derivative, Notional Amount	$ 1,000
Interest rate swap contracts \| Not Designated as Hedging Instruments \| Interest expense
Derivative [Line Items]
Loss or (Gain) Recognized on Derivatives	51	$ 39	$ 4
Interest rate swap contracts \| Other current and non-current liabilities \| Not Designated as Hedging Instruments
Derivative [Line Items]
Fair value of interest rate derivative liabilities	81	47
Interest rate swap contracts \| August 2015
Derivative [Line Items]
Derivative, Notional Amount				$ 600
Interest rate swap contracts \| November 2017
Derivative [Line Items]
Derivative, Notional Amount	450
Interest rate swap contracts \| August 2020
Derivative [Line Items]
Derivative, Notional Amount	400
Interest rate swap contracts \| November 2022
Derivative [Line Items]
Derivative, Notional Amount	150
Foreign exchange contracts \| Not Designated as Hedging Instruments \| Operating expense
Derivative [Line Items]
Loss or (Gain) Recognized on Derivatives	$ 0	$ 0	$ (1)