Segment Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($) segment
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment			2	2
Contract revenues	$ 165,985,000	$ 159,767,000	$ 309,090,000	$ 296,610,000
Marine
Segment Reporting Information [Line Items]
Contract revenues	89,023,000	80,698,000	150,510,000	143,489,000
Marine | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	2,400,000	2,400,000	2,900,000	8,300,000
Concrete
Segment Reporting Information [Line Items]
Contract revenues	76,962,000	79,069,000	158,580,000	153,121,000
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	$ 200,000	$ 100,000	$ 2,400,000	$ 2,400,000