Revenue (Summary of Type of Work, Contract Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 589,625	$ 648,781	$ 726,149
Type of Work [Member] | Operating Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	589,625	648,781	726,149
Type of Work [Member] | Operating Segment [Member] | Dredging [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	586,962	648,781	726,149
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-U.S. [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	186,715	342,461	397,034
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		149	6,596
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Coastal Protection [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	196,343	192,567	169,678
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Maintenance [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	187,586	98,077	132,551
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Rivers & Lakes [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	16,318	$ 15,527	$ 20,290
Type of Work [Member] | Operating Segment [Member] | Offshore Wind [Member]
Disaggregation Of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,663