Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment
Segment Reporting Information [Line Items]
Number of reportable segments | segment									2	2	2
Contract revenues	$ 170,176	$ 189,433	$ 183,713	$ 166,620	$ 199,793	$ 199,507	$ 165,985	$ 143,105	$ 709,942	$ 708,390	$ 520,894
Operating income (loss)	5,052	$ 13,085	$ 4,084	$ 4,365	2,701	$ 6,092	$ (423)	$ (6,177)	26,586	2,193	(100,540)
Depreciation and amortization									(23,893)	(26,096)	(31,799)
Assets	414,189				394,844				414,189	394,844
Property and equipment, net of depreciation	125,497				132,348				125,497	132,348
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues									388,173	369,138	243,883
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues									12,500	11,400
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues									321,769	339,252	$ 277,011
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									388,173	369,138
Operating income (loss)									16,935	1,057
Depreciation and amortization									(18,369)	(19,889)
Assets	290,372				264,681				290,372	264,681
Property and equipment, net of depreciation	109,298				114,873				109,298	114,873
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues									321,769	339,252
Operating income (loss)									9,651	1,136
Depreciation and amortization									(8,848)	(8,519)
Assets	123,817				130,163				123,817	130,163
Property and equipment, net of depreciation	$ 16,199				$ 17,475				16,199	17,475
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues									$ 2,800	$ 1,200