Costs And Estimated Earnings In Excess Of Billings (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Costs and estimated earnings in excess of billings [Abstract]
Claims	$ 505,069	$ 477,425
Unapproved change orders	295,204	207,475
Other unbilled costs and profits	102,039	146,926
Total costs and estimated earnings in excess of billings	$ 902,312	$ 831,826