Long-Term Debt (Narrative) (Details) - USD ($)				1 Months Ended	3 Months Ended	6 Months Ended
Long-Term Debt (Narrative) (Details) - USD ($)	Apr. 24, 2025	Apr. 24, 2024	Jul. 29, 2022	May 31, 2021	Sep. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	May 02, 2025	May 01, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Line of credit facility, net proceeds after debt issue costs						$ 80,000,000	$ 16,000,000
Debt instrument, face amount						$ 325,000,000
2029 Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 325,000,000
Debt instrument, interest rate, stated percentage				5.25%
Maturity date				Jun. 01, 2029
8.000% Senior Notes Due in 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 325,000,000
Debt instrument, interest rate, stated percentage				8.00%
Owned Domestic Subsidiaries Percent				100.00%
Debt instruments weighted average interest rate						6.80%				6.77%
Senior Notes [Member] \| 2029 Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		5.25%
Green Loan Option [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 35,000,000
Green Loan Option [Member] \| Green Loan Advance Rates [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.05%
Second Lien Credit Agreement [Member]
Debt Instrument [Line Items]
Debt		$ 150,000,000
Line of credit, remaining borrowing capacity, period		12 months
Line of credit facility, maximum borrowing capacity		$ 100,000,000
Interest expense	$ 600,000
Maximum fixed charge coverage ratio per covenant		110.00%
Loan prepayment period		18 months
Percentage of prepayment of principal loan amount		103.00%
Minimum fixed charge coverage ratio per covenant		110.00%
Maturity date		Apr. 24, 2029
Borrowings on second lien credit agreement						$ 100,000,000				$ 100,000,000
Debt instruments weighted average interest rate						12.07%
Second Lien Credit Agreement [Member] \| Prepayment After 19 To 30 Months From Closing Date [Member]
Debt Instrument [Line Items]
Percentage of prepayment of principal loan amount		103.00%
Second Lien Credit Agreement [Member] \| Prepayment After 31 To 42 Months From Closing Date [Member]
Debt Instrument [Line Items]
Percentage of prepayment of principal loan amount		101.00%
Second Lien Credit Agreement [Member] \| Senior Notes [Member] \| 2029 Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		5.25%
Second Lien Credit Agreement [Member] \| Term SOFR Loan [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		7.75%
Second Lien Credit Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000	$ 50,000,000
Amount of liquidity		12,500,000
Make-whole carveout amount		$ 25,000,000
Second Lien Credit Agreement [Member] \| Maximum [Member] \| Term SOFR Loan [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		6.75%
Second Lien Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Amount of liquidity		$ 50,000,000
Second Lien Credit Agreement [Member] \| Minimum [Member] \| Term SOFR Loan [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Second Lien Credit Agreement [Member] \| Minimum [Member] \| Federal Funds Effective Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
Percentage of quarterly fee on undrawn commitments		1.00%
ABL Amendment [Member]
Debt Instrument [Line Items]
Revolving credit facility						$ 5,000,000				35,000,000
Line of credit facility, maximum borrowing capacity		$ 200,000,000	$ 300,000,000
Letters of credit outstanding						56,300,000				43,500,000
Letter of credit remaining borrowing capacity						268,300,000				221,200,000
Maximum fixed charge coverage ratio per covenant		110.00%
Line of credit facility suppressed capacity						$ 400,000				$ 300,000
Line of credit facility, net proceeds after debt issue costs		$ 88,700,000
Minimum fixed charge coverage ratio per covenant		110.00%	110.00%
Maximum covenant percentage of undrawn availability of amended credit agreement			12.50%
Debt instrument covenant description						The springing financial covenant is triggered when the undrawn availability of the ABL Credit Agreement is less than 12.5% of the maximum loan amount for five consecutive days.
ABL Amendment [Member] \| Domestic Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.50%
ABL Amendment [Member] \| Domestic Rate [Member] \| Margin Advances Facility One [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					1.25%
ABL Amendment [Member] \| Domestic Rate [Member] \| Margin Advances Facility Two [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					1.50%
ABL Amendment [Member] \| Domestic Rate [Member] \| Margin Advances Facility Three [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					1.75%
ABL Amendment [Member] \| Term SOFR Loan [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.50%
ABL Amendment [Member] \| Term SOFR Loan [Member] \| Margin Advances Facility One [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					2.25%
ABL Amendment [Member] \| Term SOFR Loan [Member] \| Margin Advances Facility Two [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					2.50%
ABL Amendment [Member] \| Term SOFR Loan [Member] \| Margin Advances Facility Three [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate					2.75%
ABL Amendment [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Amount of liquidity		$ 12,500,000
ABL Amendment [Member] \| Maximum [Member] \| Margin Advances Facility Two [Member]
Debt Instrument [Line Items]
Maximum revolving advance amount percentage of undrawn availability of credit agreement					66.70%
ABL Amendment [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Amount of liquidity		$ 50,000,000
ABL Amendment [Member] \| Minimum [Member] \| Margin Advances Facility One [Member]
Debt Instrument [Line Items]
Maximum revolving advance amount percentage of undrawn availability of credit agreement					66.70%
ABL Amendment [Member] \| Minimum [Member] \| Margin Advances Facility Two [Member]
Debt Instrument [Line Items]
Maximum revolving advance amount percentage of undrawn availability of credit agreement					33.30%
ABL Amendment [Member] \| Minimum [Member] \| Margin Advances Facility Three [Member]
Debt Instrument [Line Items]
Maximum revolving advance amount percentage of undrawn availability of credit agreement					33.30%
ABL Second Amendment [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity								$ 330,000,000	$ 300,000,000
Debt issuance costs								$ 600,000

Great Lakes Dredge & Dock CORP 10-Q