Revenue (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Contract revenues	$ 199,793	$ 199,507	$ 165,985	$ 143,105	$ 99,211	$ 125,073	$ 159,767	$ 136,843	$ 708,390	$ 520,894	$ 578,553
Number of reportable segments | segment									2	2
Marine
Disaggregation of Revenue [Line Items]
Contract revenues									$ 369,138	$ 243,883
Marine | Construction
Disaggregation of Revenue [Line Items]
Contract revenues									242,527	156,925
Marine | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues									112,303	73,237
Marine | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues									14,308	13,721
Concrete
Disaggregation of Revenue [Line Items]
Contract revenues									339,252	277,011
Concrete | Structural
Disaggregation of Revenue [Line Items]
Contract revenues									284,624	215,628
Concrete | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues									54,497	60,926
Concrete | Other
Disaggregation of Revenue [Line Items]
Contract revenues									$ 131	$ 457