Inventories (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Inventories

	March 31, 2018			December 31, 2017
	(in thousands)
Raw materials	$	61,214		$	57,784
Work in process	3,284			5,957
Finished goods	5,391			8,163
	69,889			71,904
Less:  Allowance for excess and obsolete inventories	(1,209		)	(1,118		)
Total, net	$	68,680		$	70,786

Inventories (Allowance)

The related changes in the allowance for excess and obsolete inventories account are as follows:

	Three months ended
	March 31, 2018			March 31, 2017
Allowance for excess and obsolete inventories:	(in thousands)
Balance, beginning of period	$	1,118		$	1,382
Provisions for excess and obsolete inventories	101			60
Inventories written off	(10		)	—
Balance, end of period	$	1,209		$	1,442