Costs And Estimated Earnings In Excess Of Billings (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Costs and estimated earnings in excess of billings [Abstract]
Claims	$ 464,220	$ 477,425
Unapproved change orders	250,114	207,475
Other unbilled costs and profits	126,426	146,926
Total costs and estimated earnings in excess of billings	$ 840,760	$ 831,826