Accounts Receivable

12 Months Ended

Dec. 31, 2015

The following table presents details of our accounts receivable balances:



	As of December 31,
	2015			2014
	(Dollars in millions)
Trade and purchased receivables	$	620		649
Earned and unbilled receivables	111			120
Other	4			9
Total accounts receivable	735			778
Less: allowance for doubtful accounts	(47		)	(38	)
Accounts receivable, less allowance	$	688		740

We are exposed to concentrations of credit risk from residential and business customers within our local service area and from other telecommunications service providers. No customers individually represented more than 10% of our accounts receivable for all periods presented herein. We generally do not require collateral to secure our receivable balances. We have agreements with other telecommunications service providers whereby we agree to bill and collect on their behalf for services rendered by those providers to our customers within our local service area. We purchase accounts receivable from other telecommunications service providers primarily on a recourse basis and include these amounts in our accounts receivable balance. We have not experienced any significant loss associated with these purchased receivables.

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



	Beginning Balance		Additions	Deductions		Ending Balance
	(Dollars in millions)
2015	$	38	78	(69	)	47
2014	$	43	64	(69	)	38
2013	$	46	65	(68	)	43