Segment Information (Details)	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
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2	2	2
Contract revenues	$ 199,507,000	$ 125,073,000	$ 508,597,000	$ 421,682,000
Marine
Segment Reporting Information [Line Items]
Contract revenues	107,404,000	63,479,000	257,914,000	206,967,000
Marine | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	4,600,000	2,000,000	7,500,000	10,300,000
Concrete
Segment Reporting Information [Line Items]
Contract revenues	92,103,000	61,594,000	250,683,000	214,715,000
Concrete | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	0	0	0	0
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 300,000		$ 500,000	$ 2,400,000
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues		$ 100,000