Revenue (Summary of Impact of Change in Accounting Principle on Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract revenues	$ 620,795	$ 592,159	$ 637,468
Type of Revenue [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Costs of contract revenues	$ 509,335	$ 549,429	$ 552,130
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Income tax provision (benefit) from continuing operations	$ 5,437	$ (33,761)	$ (177)
Loss from continuing operations	11,016	(15,368)	542
Net loss	(6,293)	(31,260)	(8,177)
Comprehensive loss	(10,105)	$ (30,112)	$ (7,339)
ASU 2014-09 [Member] \| Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract revenues	$ (14,696)
Type of Revenue [Extensible List]	gldd:ContractMember
Costs of contract revenues	$ (11,360)
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember
Income tax provision (benefit) from continuing operations	$ 867
Loss from continuing operations	(2,469)
Net loss	(2,469)
Comprehensive loss	$ (2,469)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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