Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($) segment	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2
Contract revenues	$ 153,309	$ 166,620
Operating income	2,055	4,365
Depreciation and amortization	(5,704)	(6,192)
Assets	394,855		$ 414,189
Property and equipment, net of depreciation	120,879		$ 125,497
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	72,146	85,949
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	2,400	4,000
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,163	80,671
Commercial Concrete Segment | Foreign
Segment Reporting Information [Line Items]
Contract revenues	0	0
Operating Segments | Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	72,146	85,949
Operating income	(9)	2,855
Depreciation and amortization	(4,358)	(4,776)
Assets	268,345	255,311
Property and equipment, net of depreciation	106,071	112,384
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,163	80,671
Operating income	2,064	1,510
Depreciation and amortization	(2,127)	(2,116)
Assets	126,510	129,509
Property and equipment, net of depreciation	14,808	16,731
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues		$ 2,300
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues	$ 100