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Commitments and Contingencies - Asset Retirement Obligations (Details) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Loss Contingencies [Line Items]    
Asset retirement obligation $ 14 $ 14
Accrued expenses and other current liabilities    
Loss Contingencies [Line Items]    
Asset retirement obligation 2 2
Deferred credits and other liabilities    
Loss Contingencies [Line Items]    
Asset retirement obligation $ 12 $ 12