Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 298,090	$ 300,601
Less: accumulated depreciation	(189,014)	(181,293)
Net book value of depreciable assets	109,076	119,308
Property and equipment, net	148,779	158,082
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,100	2,525
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	37,928	37,269
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	164,843	165,023
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	85,569	88,659
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,650	7,125
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,416	543
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38,287	$ 38,231