Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($) segment	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($) segment	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2	2	2
Contract revenues	$ 189,433	$ 199,507	$ 539,766	$ 508,597
Operating income (loss)	13,085	6,092	21,534	(508)
Depreciation and amortization			(18,175)	(19,609)
Assets	382,520		382,520		$ 394,844
Property and equipment, net of depreciation	125,911		125,911		$ 132,348
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	112,881	107,404	290,549	257,914
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	1,800	4,600	9,700	7,500
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	76,552	92,103	249,217	250,683
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	112,881	107,404	290,549	257,914
Operating income (loss)	8,992	4,863	12,443	(1,584)
Depreciation and amortization	(4,543)	(4,960)	(14,063)	(14,975)
Assets	258,894	252,995	258,894	252,995
Property and equipment, net of depreciation	109,522	117,071	109,522	117,071
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	76,552	92,103	249,217	250,683
Operating income (loss)	4,093	1,229	9,091	1,076
Depreciation and amortization	(2,223)	(2,120)	(6,599)	(6,367)
Assets	123,626	124,112	123,626	124,112
Property and equipment, net of depreciation	16,389	16,985	16,389	16,985
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues		$ 300	$ 2,700	$ 500
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues	$ 100