Accounts Receivable, Net

12 Months Ended

Dec. 31, 2015

Receivables [Abstract]

Accounts Receivable, Net

2.    Accounts Receivable, Net

Accounts receivable, net balances at December 31, 2015 and 2014 were as follows (in thousands

	2015			2014
Trade accounts receivable	$	118,916		$	107,174
Unbilled revenue, at net realizable value		47,351			47,789
Total accounts receivable		166,267			154,963
Allowance for doubtful accounts		(12,659	)		(11,915	)
Accounts receivable, net	$	153,608		$	143,048

Changes in the allowance for doubtful accounts on accounts receivable are as follows (in thousands):

	2015			2014			2013
Balance at beginning of period	$	(11,915	)	$	(9,975	)	$	(11,363	)
Provision for losses		(5,804	)		(5,740	)		(4,664	)
Charge-offs, net of recoveries		5,060			3,800			6,052
Balance at end of period	$	(12,659	)	$	(11,915	)	$	(9,975	)