Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Schedule of Accounts Receivable

Accounts receivable at December 31 consisted of the following (in thousands):

	2017			2016
Trade accounts receivable	$	78,858		$	81,193
Contract receivables:
Amounts billed	61,351			41,569
Costs in excess of billings	11,610			6,582
Total contract receivables	72,961			48,151
Total accounts receivables	151,819			129,344
Less allowance for doubtful accounts	(6,434		)	(5,272		)
Accounts receivable	$	145,385		$	124,072