Accounts Receivable

12 Months Ended

Dec. 31, 2019

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, 2019 and 2018 (in thousands):

	December 31, 2019			December 31, 2018
Trade accounts receivable	$	396,204		$	337,445
Unbilled accounts receivable	157,619			143,978
Gross accounts receivable	553,823			481,423
Allowance for doubtful accounts and other reserves	(1,880		)	(1,534		)
Accounts receivable, net	$	551,943		$	479,889

A summary of activity in the accounts receivable reserves for the years ended December 31, 2019, 2018 and 2017 is as follows (in thousands):

	2019			2018			2017
Beginning balance	$	1,534		$	1,281		$	925
Charges to income from operations	5,116			3,824			3,407
Collections from customers previously reserved and other	(4,770		)	(3,571		)	(3,051		)
Ending balance	$	1,880		$	1,534		$	1,281

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