Summary of Significant Accounting Policies - Schedule of costs and estimated earnings on uncompleted contracts and related amounts billed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Costs incurred on uncompleted contracts	$ 8,258,802	$ 7,223,436
Estimated earnings, thereon	1,081,509	827,799
Costs and estimated earnings on uncompleted contracts	9,340,311	8,051,235
Less: billings to date	9,741,846	8,409,780
Net billings in excess of costs	(401,535)	(358,545)
Costs and estimated earnings in excess of billings on uncompleted contracts	122,621	130,697	$ 117,734
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (524,156)	$ (489,242)	$ (429,235)