Accounts Receivable

12 Months Ended

Dec. 31, 2020

Receivables [Abstract]

Accounts Receivable

Accounts Receivable

The following table presents details of our accounts receivable balances:

	Years Ended December 31,
	2020		2019
	(Dollars in millions)
Trade receivables	$	570	529
Earned and unbilled receivables	158		151
Total accounts receivable	728		680
Less: allowance for credit losses	(45)		(13)
Accounts receivable, less allowance	$	683	667

We are exposed to concentrations of credit risk from our customers and other telecommunications service providers. We generally do not require collateral to secure our receivable balances.

The following table presents details of our allowance for credit losses:

	Beginning Balance		Additions	Deductions	Ending Balance
	(Dollars in millions)
2020 (1)	$	13	41	(9)	45
2019	11		24	(22)	13
2018	3		18	(10)	11

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(1)On January 1, 2020, we adopted ASU 2016-13 "Measurement of Credit Losses on Financial Instruments" and recognized a cumulative adjustment to our accumulated deficit as of the date of adoption of $3 million, net of $2 million tax effect. This adjustment is included within "Deductions". Please refer to Note 5—Credit Losses on Financial Instruments for more information.