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ACCOUNTS RECEIVABLE - NET
 6 Months Ended
Jun. 30, 2021
Receivables [Abstract]  
Accounts Receivable - Net
June 30, 2021December 31, 2020
Trade$7,150 $7,029 
Less - Allowance for doubtful accounts(203)(202)
 $6,947 $6,827 
Trade receivables include $1,830 million and $1,589 million of unbilled balances under long-term contracts as of June 30, 2021, and December 31, 2020. These amounts are billed in accordance with the terms of the customer contracts to which they relate.