Operating Segments - Summarized Segment Financial Information (Parenthetical) (Details) - Forty-Vehicle Ferry $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($) Vechicle	Jun. 30, 2020 Vechicle	Jun. 30, 2019 USD ($) Vechicle
Segment Reporting Information [Line Items]
Revenue reclassified between the Shipyard and Fabrication & Services segments \| $	$ 2.5		$ 3.3
Number of vehicle ferry projects \| Vechicle	2	2	2

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