Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Accounts Receivable

Schedule of components of accounts receivables

December 31,	2017			2016
(in thousands)
Trade receivables:
Billed	$	296,588		$	122,216
Unbilled		68,494			39,223
Other receivables		17,242			10,280
Total		382,324			171,719
Less: allowance for doubtful accounts		(4,471	)		(2,553	)
Accounts receivable, net	$	377,853		$	169,166

Schedule of changes in allowance for doubtful accounts

Years Ended December 31,	2017			2016
(in thousands)
Beginning balance	$	2,553		$	10,605
Bad debt expense (reduction)		1,441			6,021
Accounts written-off		(105	)		(14,101	)
Recoveries		582			28
Ending balance	$	4,471		$	2,553