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Revenue (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenue From Contract With Customer [Line Items]
Revenue, remaining performance obligation	$ 452,587		$ 452,587
Performance obligations exclude from dredging backlog	$ 50,000		$ 50,000
Percentage of performance obligation to be recognized as revenue			38.00%
Performance obligation, expected to be recognized as revenue year			2022
Remaining performance obligation, expected timing of satisfaction, year	2023		2023
Increased gross profit	$ 4,880		$ 22,242
Amortization on pre-construction costs	2,856	$ 3,687	7,308	$ 15,443
Other Current and Noncurrent Assets [Member]
Revenue From Contract With Customer [Line Items]
Costs to fulfill a contract with customer recognized as an asset	$ 5,450		$ 5,450		$ 5,652

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- Definition

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- Definition

Performance obligation expected to be recognized as revenue, year.

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126905575&loc=SL49131252-203054

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126905575&loc=SL49131252-203054

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

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