Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 300,654	$ 300,601
Less: accumulated depreciation	(188,996)	(181,293)
Net book value of depreciable assets	111,658	119,308
Property and equipment, net	151,501	158,082
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,219	2,525
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	37,277	37,269
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	164,373	165,023
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	89,313	88,659
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,472	7,125
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,612	543
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38,231	$ 38,231