Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 290,763	$ 286,480
Less: accumulated depreciation	(172,950)	(164,371)
Net book value of depreciable assets	117,813	122,109
Property and equipment, net	164,384	165,989
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,506	2,749
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	31,374	28,226
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	164,880	159,963
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	84,992	89,485
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,011	6,057
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,340	5,649
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38,231	$ 38,231