Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment			2
Contract revenues	$ 125,073	$ 140,162	$ 421,682	$ 416,339
Marine
Segment Reporting Information [Line Items]
Contract revenues	63,479		206,967
Marine | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	2,000	$ 3,000	10,300	$ 3,900
Concrete
Segment Reporting Information [Line Items]
Contract revenues	61,594		214,715
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 100		$ 2,400