Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 281,966		$ 281,966		$ 277,901
Less: accumulated depreciation	(168,782)		(168,782)		(161,276)
Net book value of depreciable assets	113,184		113,184		116,625
Property and equipment, net	158,642		158,642		161,773
Depreciation expense	5,200	$ 5,600	10,600	$ 11,200
Automobiles and trucks
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,967		1,967		2,006
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	31,480		31,480		28,641
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	147,417		147,417		146,088
Dredges and dredging equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	95,979		95,979		96,275
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,123		5,123		4,891
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,584		5,584		5,274
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 39,874		$ 39,874		$ 39,874