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Commitments and Contingencies Commitments and Contingencies (European Commission Investigation) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		9 Months Ended
	Jan. 12, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period		$ 0	$ 2	$ 0	$ 2
Other Noncurrent Liabilities [Member] \| Cash Flow Hedging [Member] \| Fair Value, Recurring [Member] \| Designated as Hedging Instrument [Member]
Loss Contingencies [Line Items]
Interest rate swaps		$ (64)		$ (64)			$ (81)
European Commission Competition Law Investigation
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss								$ 89
European Commission Competition Law Investigation \| Settled Litigation
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period						$ 92
Loss contingency accrual, carrying value, payments	$ 100