RECEIVABLES

12 Months Ended

May 31, 2014

RECEIVABLES

3. RECEIVABLES

A summary of accounts receivable as of May 31, 2014 and 2013 is as follows (in thousands):

	May 31,
	2014			2013
Trade accounts receivable	$	165,484		$	152,030
Unbilled revenues		14,901			25,516
Allowance for doubtful accounts		(4,784	)		(5,438	)
Total	$	175,601		$	172,108

The allowance for doubtful accounts is our best estimate of the amount of probable credit losses in our existing accounts receivable. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is remote. The following summarizes the activity in the allowance for doubtful accounts as of May 31, 2014, 2013 and 2012 (in thousands):

	Twelve Months Ended May 31,
	2014			2013			2012
Balance at beginning of year	$	5,438		$	4,405		$	4,222
Provision for doubtful accounts		2,140			2,922			1,650
Write-off of bad debts		(2,794	)		(1,889	)		(1,467	)
Balance at end of year	$	4,784		$	5,438		$	4,405