Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Contract revenues	$ 136,843	$ 138,757
Marine
Disaggregation of Revenue [Line Items]
Contract revenues	62,791
Marine | Construction
Disaggregation of Revenue [Line Items]
Contract revenues	42,375
Marine | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues	17,011
Marine | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues	3,405
Concrete
Disaggregation of Revenue [Line Items]
Contract revenues	74,052
Concrete | Structural
Disaggregation of Revenue [Line Items]
Contract revenues	17,372
Concrete | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues	56,493
Concrete | Other
Disaggregation of Revenue [Line Items]
Contract revenues	$ 187