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Segment Information (Details) $ in Thousands	3 Months Ended		12 Months Ended	15 Months Ended
Segment Information (Details) $ in Thousands	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	2
Contract revenues	$ 166,620	$ 143,105
Operating income (loss)	4,365	(6,177)
Depreciation and amortization	(6,192)	(6,471)
Assets	384,820		$ 394,844	$ 384,820
Property and equipment, net of depreciation	129,115		132,348	129,115
Marine
Segment Reporting Information [Line Items]
Contract revenues	85,949	61,487
Marine \| Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	4,000	500
Concrete
Segment Reporting Information [Line Items]
Contract revenues	80,671	81,618
Concrete \| Foreign
Segment Reporting Information [Line Items]
Contract revenues	0		$ 0
Operating Segments \| Marine
Segment Reporting Information [Line Items]
Contract revenues	85,949	61,487
Operating income (loss)	2,855	(6,456)
Depreciation and amortization	(4,776)	(4,946)
Assets	255,311	213,162		255,311
Property and equipment, net of depreciation	112,384	118,596		112,384
Operating Segments \| Concrete
Segment Reporting Information [Line Items]
Contract revenues	80,671	81,618
Operating income (loss)	1,510	279
Depreciation and amortization	(2,116)	(2,094)
Assets	129,509	127,220		129,509
Property and equipment, net of depreciation	16,731	$ 18,245		16,731
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues	$ 2,300			$ 100