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Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Valuation and Qualifying Accounts      
Balance at beginning of period $ 54 $ 40 $ 16
Additions Charged to Costs and Expenses 49 20 30
Deductions 5 6 6
Balance at end of period 98 54 40
Valuation allowance for deferred tax assets      
Valuation and Qualifying Accounts      
Balance at beginning of period 31 21 1
Additions Charged to Costs and Expenses 38 10 20
Deductions 0 0 0
Balance at end of period 69 31 21
Allowance for obsolete inventory parts      
Valuation and Qualifying Accounts      
Balance at beginning of period 22 18 14
Additions Charged to Costs and Expenses 5 4 4
Deductions 0 0 0
Balance at end of period 27 22 18
Allowance for doubtful accounts      
Valuation and Qualifying Accounts      
Balance at beginning of period 1 1 1
Additions Charged to Costs and Expenses 6 6 6
Deductions 5 6 6
Balance at end of period $ 2 $ 1 $ 1