We maintain an allowance for doubtful accounts that reflects our best estimate of potentially uncollectible trade receivables. The allowance is based on assessments of the collectability of specific customer accounts and the general aging and size of the accounts receivable. We regularly review the adequacy of our allowance for doubtful accounts by considering such factors as historical experience, credit worthiness, and current economic conditions that may affect a customer's ability to pay. We specifically reserve for those accounts deemed uncollectible. We also establish, and adjust, a general allowance for doubtful accounts based on our review of the aging and size of our accounts receivable. The following table sets forth the details of the Allowance for Doubtful Accounts for the three and nine-month periods ended September 30, 2012 and 2011:

	Beginning Balance		Charge Offs		Recoveries		Provision			Ending Balance
Three Months Ended September 30,
2012	$	37,900	$	—	$	—	$	(7,700	)	$	30,200
2011		28,400		—		—		(1,600	)		26,800
Nine Months Ended September 30,
2012	$	25,000	$	—	$	—	$	5,200		$	30,200
2011		32,800		—		—		(6,000	)		26,800