Accounts Receivable

12 Months Ended

Dec. 31, 2018

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, 2018 and 2017 (in thousands):

	December 31, 2018			December 31, 2017
Trade accounts receivable	$	337,445		$	320,001
Unbilled accounts receivable	143,978			142,737
Gross accounts receivable	481,423			462,738
Allowance for doubtful accounts and other reserves	(1,534		)	(1,281		)
Accounts receivable, net	$	479,889		$	461,457

A summary of activity in the accounts receivable reserves for the years ended December 31, 2018, 2017 and 2016 is as follows (in thousands):

	2018			2017			2016
Beginning balance	$	1,281		$	925		$	1,019
Charges to income from operations	3,824			3,407			2,099
Collections from customers previously reserved and other	(3,571		)	(3,051		)	(2,193		)
Ending balance	$	1,534		$	1,281		$	925

Charges to income from operations primarily represents charges to bad debt expense for increases in the allowance for doubtful accounts.