Summary of Significant Accounting Policies - Depreciable Lives of Property and Equipment (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense									$ 28,400	$ 24,800	$ 26,900
Net (loss) income									$ (94,422)	$ 400	$ (3,620)
Diluted (in dollars per share)	$ (3.32)	$ (0.22)	$ 0.08	$ 0.14	$ 0.34	$ (0.18)	$ (0.08)	$ (0.07)	$ (3.31)	$ 0.01	$ (0.13)
Automobiles and trucks | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									3 years
Automobiles and trucks | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									5 years
Building and improvements | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									5 years
Building and improvements | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									30 years
Construction equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									3 years
Construction equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									15 years
Dredges and dredging equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									1 year
Dredges and dredging equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									15 years
Office equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									1 year
Office equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									5 years
Dry-docking capitalized costs | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									3 years
Dry-docking capitalized costs | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment useful life									15 years