Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 295,201		$ 295,201		$ 304,728
Less: accumulated depreciation	(197,340)		(197,340)		(195,373)
Net book value of depreciable assets	97,861		97,861		109,355
Property and equipment, net of depreciation	135,045		135,045		148,003
Depreciation	6,000	$ 6,600	11,800	$ 12,500
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,669		1,669		1,709
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	43,790		43,790		43,628
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	158,684		158,684		161,113
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	82,875		82,875		90,217
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,183		8,183		8,061
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,321		1,321		2,785
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 35,863		$ 35,863		$ 35,863