Segment Information (Details)	3 Months Ended			6 Months Ended
	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment				2
Contract revenues	$ 137,420,000		$ 140,301,000		$ 269,924,000
Marine Construction | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	800,000		$ 3,700,000	$ 900,000	$ 6,100,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 0	$ 0		$ 0