Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($) segment	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($) segment	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2	2	2
Contract revenues	$ 139,907	$ 189,433	$ 439,091	$ 539,766
Operating income (loss)	(8,743)	13,085	(1,122)	21,534
Depreciation and amortization			(16,881)	(18,175)
Assets	368,355		368,355		$ 414,189
Property and equipment, net of depreciation	106,685		106,685		$ 125,497
Marine Segment
Segment Reporting Information [Line Items]
Contract revenues	54,739	112,881	190,827	290,549
Operating income (loss)	(4,965)	12,025	6,489	21,584
Depreciation and amortization	(4,232)	(4,543)	(12,912)	(14,063)
Assets	252,332	258,894	252,332	258,894
Property and equipment, net of depreciation	92,612	109,522	92,612	109,522
Marine Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues		1,800	2,800	9,700
Marine Segment | Mexico and the Caribbean | Maximum
Segment Reporting Information [Line Items]
Contract revenues	100
Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	85,168	76,552	248,264	249,217
Concrete Segment | Foreign
Segment Reporting Information [Line Items]
Contract revenues	0	0	0	0
Operating Segments | Marine Segment | Revision of Prior Period, Error Correction, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)		3,000	2,900	9,200
Operating Segments | Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	85,168	76,552	248,264	249,217
Operating income (loss)	(3,778)	1,060	(7,611)	(50)
Depreciation and amortization	(1,993)	(2,223)	(6,228)	(6,599)
Assets	116,023	123,626	116,023	123,626
Property and equipment, net of depreciation	14,073	16,389	14,073	16,389
Operating Segments | Concrete Segment | Revision of Prior Period, Error Correction, Adjustment
Segment Reporting Information [Line Items]
Operating income (loss)		(3,000)	(2,900)	(9,200)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 0			$ 2,700
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues		$ 100	$ 100