Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 302,472	$ 277,901
Less: accumulated depreciation	(173,904)	(161,276)
Net book value of depreciable assets	128,568	116,625
Property and equipment, net	163,921	161,773
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,959	2,006
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	48,190	28,641
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	150,997	146,088
Dredges and dredging equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	95,753	96,275
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,573	4,891
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,088	5,274
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 34,265	$ 39,874