Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($) segment	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($) segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 199,507	$ 125,073	$ 508,597	$ 421,682
Number of reportable segments | segment	2	2	2	2
Marine
Disaggregation of Revenue [Line Items]
Contract revenues	$ 107,404	$ 63,479	$ 257,914	$ 206,967
Marine | Construction
Disaggregation of Revenue [Line Items]
Contract revenues	72,609	46,113	163,426	141,348
Marine | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues	29,404	13,053	82,762	53,536
Marine | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues	5,391	4,313	11,726	12,083
Concrete
Disaggregation of Revenue [Line Items]
Contract revenues	92,103	61,594	250,683	214,715
Concrete | Structural
Disaggregation of Revenue [Line Items]
Contract revenues	13,439	13,054	37,595	47,166
Concrete | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues	78,587	48,458	212,958	167,140
Concrete | Other
Disaggregation of Revenue [Line Items]
Contract revenues	$ 77	$ 82	$ 130	$ 409