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Schedule II - Valuation Accounts and Reserves (Details) - SEC Schedule, 12-09, Allowance, Credit Loss - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Beginning balance $ 15 $ 15 $ 13
Provision for doubtfull accounts 19 11 6
Net deductions and other 6 11 4
Ending balance $ 28 $ 15 $ 15