Segment Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 segment
Segment Reporting Information [Line Items]
Number of reportable segments (segment) | segment			2		1
Contract revenues	$ 164,017,000	$ 137,061,000	$ 433,941,000	$ 304,607,000
Heavy Civil Marine Construction | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	1,100,000	4,500,000	7,200,000	17,100,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 0	$ 0	$ 0	$ 0