Contracts in Progress (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Contractors [Abstract]
Costs incurred on uncompleted contracts	$ 871,900	$ 802,140
Estimated earnings	140,465	143,975
Costs incurred and estimated earnings on uncompleted contracts	1,012,365	946,115
Less: Billings to date	(999,487)	(933,828)
Costs and estimated earnings in excess of billings on uncompleted contracts, net	12,878	12,287
Costs and estimated earnings in excess of billings on uncompleted contracts	41,829	39,968
Billings in excess of costs and estimated earnings on uncompleted contracts	(28,951)	(27,681)
Costs and estimated earnings in excess of billings on completed contracts, net of billings (totaled less than)	$ 400	$ 600