Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories

Inventories as of December 31, 2017 and 2016 consist of the following amounts (in thousands):

	2017		2016
Raw materials and construction materials	$	23,924	$	21,997
Work in process	18,800		15,429
Inventories	$	42,724	$	37,426