Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Contract revenues	$ 99,211	$ 125,073	$ 159,767	$ 136,843	$ 162,214	$ 140,162	$ 137,420	$ 138,757	$ 520,894	$ 578,553	$ 578,236
Marine
Disaggregation of Revenue [Line Items]
Contract revenues									243,883
Marine | Construction
Disaggregation of Revenue [Line Items]
Contract revenues									156,925
Marine | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues									73,237
Marine | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues									13,721
Concrete
Disaggregation of Revenue [Line Items]
Contract revenues									277,011
Concrete | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues									215,628
Concrete | Structural
Disaggregation of Revenue [Line Items]
Contract revenues									60,926
Concrete | Other
Disaggregation of Revenue [Line Items]
Contract revenues									$ 457