Segment Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment			2
Contract revenues	$ 140,162,000	$ 164,017,000	$ 416,339,000	$ 433,941,000
Marine Construction | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	3,000,000	1,100,000	3,900,000	7,200,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 0	$ 0	$ 0	$ 0