Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 292,345	$ 286,480
Less: accumulated depreciation	(176,681)	(164,371)
Net book value of depreciable assets	115,664	122,109
Property and equipment, net	161,243	165,989
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,525	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	164,985	159,963
Vessels and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	86,402	89,485
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,059	6,057
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,348	5,649
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38,231	$ 38,231