Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2015

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

Schedule of 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

Schedule of Activity in the Accounts Receivable Reserves

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