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Revenue (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Revenue From Contract With Customer [Line Items]
Revenue, remaining performance obligation	$ 434,555		$ 434,555
Performance obligations exclude from dredging backlog	$ 50,000		$ 50,000
Percentage of performance obligation to be recognized as revenue			53.00%
Performance obligation, expected to be recognized as revenue year			2023
Remaining performance obligation, expected timing of satisfaction, year	2024 2025		2024 2025
Increased gross profit		$ 5,638		$ 17,362
Amortization on pre-construction costs	$ 1,323	$ 2,061	$ 4,989	$ 4,452
Other Current and Noncurrent Assets [Member]
Revenue From Contract With Customer [Line Items]
Costs to fulfill a contract with customer recognized as an asset	$ 7,675		$ 7,675		$ 4,472

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- Definition

Increased gross profit.

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- Definition

Percentage of performance obligation to be recognized as revenue.

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- Definition

Performance obligation expected to be recognized as revenue, year.

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- Definition

Performance obligations exclude from dredging backlog.

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- Definition

Revenue from contract with customer line items.

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- Definition

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479483/340-40-50-3

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- Definition

Amount, before accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479483/340-40-50-3

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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-SubTopic 10
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-13

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- Definition

Year in which remaining performance obligation is expected to be recognized, in YYYY format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-SubTopic 10
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-13

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