Contracts in Progress (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Contractors [Abstract]
Costs incurred on uncompleted contracts	$ 742,836	$ 742,836		$ 668,848
Estimated earnings	130,965	130,965		120,751
Costs incurred and estimated earnings on uncompleted contracts	873,801	873,801		789,599
Less: Billings-to-date	(840,918)	(840,918)		(777,516)
Costs and estimated earnings in excess of billings on uncompleted contracts, net	32,883	32,883		12,083
Costs and estimated earnings in excess of billings on uncompleted contracts	57,411	57,411	$ 47,389	46,006
Billings in excess of costs and estimated earnings on uncompleted contracts	(24,528)	(24,528)	$ (35,668)	(33,923)
Cost and estimated earnings in excess of billings on uncompleted projects	15,500	15,500		$ 15,500
Contract with customer, liability, revenue recognized	$ 4,700	$ 24,300