RECEIVABLES (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Summary of Accounts Receivable

A summary of accounts receivable as of December 31, 2017 and December 31, 2016 is as follows (in thousands):

	December 31,
	2017			2016
Trade accounts receivable	$	244,133		$	230,889
Unbilled revenues	69,138			39,719
Allowance for doubtful accounts	(11,308		)	(7,835		)
Total	$	301,963		$	262,773

Summary of Activity in Allowance for Doubtful Accounts

The following summarizes the activity in the allowance for doubtful accounts (in thousands):

	Twelve Months Ended December 31,						Seven Months Ended December 31,			Twelve Months Ended May 31,
	2017			2016			2015			2015
Balance at beginning of period	$	7,835		$	3,548		$	2,775		$	4,784
Provision for doubtful accounts	7,097			6,336			1,819			233
Write-off of bad debts	(3,624		)	(2,049		)	(1,046		)	(2,242		)
Balance at end of period	$	11,308		$	7,835		$	3,548		$	2,775