Accounts Receivable

12 Months Ended

Dec. 31, 2015

Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]

Accounts Receivable

Accounts Receivable

Net accounts receivable consisted of the following as of December 31, 2015 and 2014 (in thousands):

	December 31, 2015			December 31, 2014
Trade accounts receivable	$	262,885		$	222,531
Unbilled accounts receivable	124,878			116,070
Gross accounts receivable	387,763			338,601
Allowance for doubtful accounts	(906		)	(1,033		)
Reserve for cash-basis customers	(6,458		)	(7,990		)
Total accounts receivable reserves	(7,364		)	(9,023		)
Accounts receivable, net	$	380,399		$	329,578

A summary of activity in the accounts receivable reserves for the years ended December 31, 2015, 2014 and 2013, is as follows (in thousands):

	2015			2014			2013
Beginning balance	$	9,023		$	3,703		$	3,807
Charges to income from operations	37,870			32,293			17,900
Collections from cash basis customers and write-offs	(39,529		)	(26,973		)	(18,004		)
Ending balance	$	7,364		$	9,023		$	3,703

Charges to income from operations represent charges to bad debt expense for increases in the allowance for doubtful accounts and reductions to revenue for increases in reserves for cash basis customers.