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Revenue (Narrative) (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Performance obligations exclude from dredging backlog | $ 44,600,000 |  |
Revenue, remaining performance obligation | $ 1,040,000,000.00 |  |
Percentage of performance obligation to be recognized as revenue | 60.00% |  |
Performance obligation, expected to be recognized as revenue year | 2024 |  |
Amortization on pre-contract and pre-construction costs | $ 11,474,000 | $ 11,148,000 |
Contract revenues | 589,625,000 | 648,781,000 | $ 726,149,000
Long-lived assets, net book value | $ 0 | 0 |
Increased gross profit |  | $ 22,276,000 |
Dredging [Member] | Use of Equipment [Member] | Federal Government [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Contract revenues |  |  | $ 716,000
Dredging [Member] | Sales [Member] | Geographic Concentration Risk [Member] | Middle East [Member] | Maximum [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Concentration risk percentage | 1.00% | 1.00% | 1.00%
Dredging [Member] | Sales [Member] | Federal Government Agencies [Member] | Customer Concentration Risk [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Concentration risk percentage | 75.00% | 67.00% | 78.00%
Dredging [Member] | Accounts Receivable [Member] | Geographic Concentration Risk [Member] | Middle East [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Concentration risk percentage | 0.00% | 9.00% |
Dredging [Member] | Accounts Receivable [Member] | Federal Government Agencies [Member] | Customer Concentration Risk [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Concentration risk percentage | 36.00% | 46.00% |
Other Current Assets [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Costs to fulfill contracts with customers recognized as an asset | $ 18,138,000 | $ 4,472,000 |
Other Noncurrent Assets [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Costs to fulfill contracts with customers recognized as an asset | $ 4,028,000 | $ 0 |

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