Business Combinations And Dispositions Unaudited Pro Forma) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue as reported	$ 856,878	$ 806,831	$ 731,418
Revenue of purchased businesses for the period prior to the acquisition		106,723	87,943
Pro forma revenue		913,554	819,361
Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$ (6,189)	10,295	(34,361)
Net income of Magnus including net income prior to acquisition and pro forma acquisition accounting adjustments		6,328	1,069
Pro forma net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		16,623	(33,292)
As Reported [Member]
Revenue as reported		806,831	731,418
GLDD Corporation [Member]
Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		$ 10,295	$ (34,361)