Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment
Property, plant and equipment, gross	$ 292,260	$ 304,728
Less: accumulated depreciation	(196,973)	(195,373)
Property, plant and equipment net book value of depreciable assets	95,287	109,355
Property and equipment, net of depreciation	132,348	148,003
Automobiles and trucks
Property, Plant and Equipment
Property, plant and equipment, gross	2,161	1,709
Building and improvements
Property, Plant and Equipment
Property, plant and equipment, gross	44,278	43,628
Construction equipment
Property, Plant and Equipment
Property, plant and equipment, gross	153,147	161,113
Vessels and other equipment
Property, Plant and Equipment
Property, plant and equipment, gross	84,022	90,217
Office equipment
Property, Plant and Equipment
Property, plant and equipment, gross	8,652	8,061
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, gross	1,198	2,785
Land
Property, Plant and Equipment
Property, plant and equipment, gross	$ 35,863	35,863
Assets Held under Capital Leases [Member]
Property, Plant and Equipment
Property and equipment, net of depreciation		$ 9,200