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Commitments and Contingencies (Narrative) (Details)	Sep. 30, 2025 USD ($)
Commitments And Contingencies [Line Items]
Outstanding performance bonds	$ 1,200,000,000
Revenue value remaining from outstanding performance bonds	664,700,000
Minimum [Member]
Commitments And Contingencies [Line Items]
Bids bond range	1,000,000
Maximum [Member]
Commitments And Contingencies [Line Items]
Bids bond range	$ 10,000,000

X

- Definition

Bids bond range.

+ References

No definition available.

+ Details

Name:	gldd_BidsBondRange
Namespace Prefix:	gldd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Commitments and contingencies.

+ References

No definition available.

+ Details

Name:	gldd_CommitmentsAndContingenciesLineItems
Namespace Prefix:	gldd_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Outstanding performance bonds.

+ References

No definition available.

+ Details

Name:	gldd_OutstandingPerformanceBonds
Namespace Prefix:	gldd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Revenue value remaining from outstanding performance bonds.

+ References

No definition available.

+ Details

Name:	gldd_RevenueValueRemainingFromOutstandingPerformanceBonds
Namespace Prefix:	gldd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: