Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Schedule of the entity's accounts receivable balances

The following table presents details of our accounts receivable balances:

	As of December 31,
	2017			2016
	(Dollars in millions)
Trade and purchased receivables	$	591		634
Earned and unbilled receivables	99			115
Other	3			4
Total accounts receivable	693			753
Less: allowance for doubtful accounts	(47		)	(53	)
Accounts receivable, less allowance	$	646		700

Schedule of the entity's allowance for doubtful accounts

The following table presents details of our allowance for doubtful accounts:

	Beginning Balance		Additions	Deductions		Ending Balance
	(Dollars in millions)
2017	$	53	74	(80	)	47
2016	$	47	80	(74	)	53
2015	$	38	78	(69	)	47