Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 298,163	$ 300,601
Less: accumulated depreciation	(184,013)	(181,293)
Net book value of depreciable assets	114,150	119,308
Property and equipment, net	153,916	158,082
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,277	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	162,633	165,023
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	88,659	88,659
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,317	7,125
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,535	543
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38,231	$ 38,231