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ACCOUNTS RECEIVABLE - NET
9 Months Ended
Sep. 30, 2021
Receivables [Abstract]  
Accounts Receivable - Net
September 30, 2021December 31, 2020
Trade$7,427 $7,029 
Less - Allowance for doubtful accounts(188)(202)
 $7,239 $6,827 
Trade receivables include $2,049 million and $1,589 million of unbilled balances under long-term contracts as of September 30, 2021, and December 31, 2020. These amounts are billed in accordance with the terms of the customer contracts to which they relate.