Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment			2
Contract revenues	$ 159,767	$ 137,420	$ 296,610	$ 276,177
Marine
Segment Reporting Information [Line Items]
Contract revenues	80,698		143,489
Marine | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	2,400	$ 800	8,300	$ 900
Concrete
Segment Reporting Information [Line Items]
Contract revenues	$ 79,069		153,121
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues			$ 2,400