Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Contract revenues	$ 143,105	$ 136,843
Marine
Disaggregation of Revenue [Line Items]
Contract revenues	61,487	62,791
Marine | Construction
Disaggregation of Revenue [Line Items]
Contract revenues	33,636	42,375
Marine | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues	26,167	17,011
Marine | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues	1,684	3,405
Concrete
Disaggregation of Revenue [Line Items]
Contract revenues	81,618	74,052
Concrete | Structural
Disaggregation of Revenue [Line Items]
Contract revenues	11,491	17,372
Concrete | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues	70,096	56,493
Concrete | Other
Disaggregation of Revenue [Line Items]
Contract revenues	$ 31	$ 187