Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($) segment	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($) segment	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2	2	2
Contract revenues	$ 145,875	$ 183,713	$ 299,184	$ 350,333
Operating income	5,566	4,084	7,621	8,449
Depreciation and amortization			(11,313)	(12,311)
Assets	383,205		383,205		$ 414,189
Property and equipment, net of depreciation	104,917		104,917		$ 125,497
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	63,942	91,719	136,088	177,668
Operating income	8,606	3,810	11,454	9,559
Depreciation and amortization	(4,322)	(4,744)	(8,680)	(9,520)
Assets	253,658	233,326	253,658	233,326
Property and equipment, net of depreciation	90,961	111,416	90,961	111,416
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	400	3,900	2,800	7,900
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,933	91,994	163,096	172,665
Commercial Concrete Segment | Foreign
Segment Reporting Information [Line Items]
Contract revenues	0	0	0	0
Operating Segments | Heavy Civil Marine Construction Segment | Revision of Prior Period, Error Correction, Adjustment
Segment Reporting Information [Line Items]
Operating income		3,200	2,900	6,100
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,933	91,994	163,096	172,665
Operating income	(3,040)	274	(3,833)	(1,110)
Depreciation and amortization	(2,107)	(2,260)	(4,235)	(4,376)
Assets	129,547	138,095	129,547	138,095
Property and equipment, net of depreciation	13,956	15,555	13,956	15,555
Operating Segments | Commercial Concrete Segment | Revision of Prior Period, Error Correction, Adjustment
Segment Reporting Information [Line Items]
Operating income		(3,200)	(2,900)	(6,100)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues		$ 400		$ 2,700
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues	$ 100		$ 100