Segment Information - Summary (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Contract revenues	$ 137,420	$ 140,301		$ 269,924
Operating loss	(2,466)	281		(174)
Depreciation and amortization expense			$ (15,119)	(17,203)
Total Assets	426,472		426,472		$ 447,676
Property and equipment, net	151,501		151,501		$ 158,082
Operating Segments | Marine Construction
Segment Reporting Information [Line Items]
Contract revenues	62,003	79,966	129,183	142,381
Operating loss	(8,617)	(1,212)	(16,323)	(4,354)
Depreciation and amortization expense	(5,087)	(5,176)	(10,342)	(10,243)
Total Assets	252,348	297,207	252,348	297,207
Property and equipment, net	135,492	149,912	135,492	149,912
Operating Segments | Concrete Construction
Segment Reporting Information [Line Items]
Contract revenues	75,417	60,335	146,994	127,543
Operating loss	6,150	1,493	12,375	4,180
Depreciation and amortization expense	(2,505)	(3,477)	(4,777)	(6,960)
Total Assets	174,124	146,127	174,124	146,127
Property and equipment, net	$ 16,009	$ 14,472	$ 16,009	$ 14,472