Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Property, plant and equipment, gross	$ 265,910	$ 268,224
Less: accumulated depreciation	(198,058)	(195,948)
Property, plant and equipment net book value of depreciable assets	67,852	72,276
Property and equipment, net of depreciation	97,307	100,977
Automobiles and trucks
Property, Plant and Equipment
Property, plant and equipment, gross	2,243	2,232
Building and improvements
Property, Plant and Equipment
Property, plant and equipment, gross	36,953	36,952
Construction equipment
Property, Plant and Equipment
Property, plant and equipment, gross	129,883	130,660
Vessels and other equipment
Property, Plant and Equipment
Property, plant and equipment, gross	89,946	91,495
Office equipment
Property, Plant and Equipment
Property, plant and equipment, gross	6,885	6,885
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, gross	1,570	816
Land
Property, Plant and Equipment
Property, plant and equipment, gross	$ 27,885	$ 27,885

Property, Plant and Equipment, Net Book Value of Depreciable Assets

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Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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