Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($) segment	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($) segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 139,907	$ 189,433	$ 439,091	$ 539,766
Number of reportable segments | segment	2	2	2	2
Marine Segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 54,739	$ 112,881	$ 190,827	$ 290,549
Marine Segment | Construction
Disaggregation of Revenue [Line Items]
Contract revenues	38,883	86,505	121,678	205,459
Marine Segment | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues	13,157	24,262	58,511	79,391
Marine Segment | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues	2,699	2,114	10,638	5,699
Concrete Segment
Disaggregation of Revenue [Line Items]
Contract revenues	85,168	76,552	248,264	249,217
Concrete Segment | Structural
Disaggregation of Revenue [Line Items]
Contract revenues	13,090	21,116	47,296	66,893
Concrete Segment | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues	$ 72,078	$ 55,436	200,961	182,311
Concrete Segment | Other
Disaggregation of Revenue [Line Items]
Contract revenues			$ 7	$ 13