Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($) segment	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($) segment	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2	2	2
Contract revenues	$ 183,713	$ 165,985	$ 350,333	$ 309,090
Operating income (loss)	4,084	(423)	8,449	(6,600)
Depreciation and amortization			(12,311)	(13,108)
Assets	371,421		371,421		$ 394,844
Property and equipment, net of depreciation	126,971		126,971		$ 132,348
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	91,719	89,023	177,668	150,510
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	3,900	2,400	7,900	2,900
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	91,994	76,962	172,665	158,580
Commercial Concrete Segment | Foreign
Segment Reporting Information [Line Items]
Contract revenues	0	0	0	0
Operating Segments | Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	91,719	89,023	177,668	150,510
Operating income (loss)	596	9	3,451	(6,447)
Depreciation and amortization	(4,744)	(5,069)	(9,520)	(10,015)
Assets	233,326	236,917	233,326	236,917
Property and equipment, net of depreciation	111,416	117,262	111,416	117,262
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	91,994	76,962	172,665	158,580
Operating income (loss)	3,488	(432)	4,998	(153)
Depreciation and amortization	(2,260)	(2,153)	(4,376)	(4,247)
Assets	138,095	125,872	138,095	125,872
Property and equipment, net of depreciation	15,555	17,783	15,555	17,783
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 400	$ 200	$ 2,700	$ 100