Quarterly report pursuant to Section 13 or 15(d)

Revenue, Contract Assets and Liabilities and Other Contract Matters - Additional Information (Details)

v3.20.2
Revenue, Contract Assets and Liabilities and Other Contract Matters - Additional Information (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Vechicle
Sep. 30, 2020
USD ($)
Vechicle
Project
Sep. 30, 2019
USD ($)
Vechicle
Mar. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
USD ($)
Dec. 31, 2017
USD ($)
Long Term Contracts Or Programs Disclosure [Line Items]                
Reduction of estimated contract price for liquidated damages, amount $ 11.6   $ 11.6       $ 12.9 $ 11.2
Hurricane Laura                
Long Term Contracts Or Programs Disclosure [Line Items]                
Date of landfall     2020-08          
Impact of Hurricane Laura, description     In August 2020, Hurricane Laura made landfall as a high-end Category 4 hurricane in Lake Charles, Louisiana, where its high winds and flooding caused significant damage throughout the region. At our Lake Charles Yard, Hurricane Laura primarily damaged drydocks, warehouses, bulkheads and our ninth harbor tug project which was nearing completion (and subsequently was completed in October 2020).          
Deductible charges associated with, description     As a result, during both the three and nine months ended September 30, 2020, we recorded charges totaling $1.2 million related to deductibles associated with our builder’s risk, equipment, property and marine liability insurance coverages, and our preliminary estimates of cost associated with uninsurable damage, primarily for bulkheads.          
Other (income) expense, net | Hurricane Laura                
Long Term Contracts Or Programs Disclosure [Line Items]                
Total charges related to deductibles 1.2   $ 1.2          
Shipyard                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins 6.7 $ 2.4 8.7 $ 4.4        
Fabrication & Services                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins 0.6 1.5 2.6 1.4        
Harbor Tug                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins   1.9 $ 0.6 3.1        
Number of vehicle ferry projects | Vechicle     2          
Reserve for loss 0.3 $ 1.9 $ 0.3 $ 1.9        
Forty-Vehicle Ferry                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins     $ 1.3          
Number of vehicle ferry projects | Vechicle   2 2 2        
Reserve for loss 2.0   $ 2.0          
Forty-Vehicle Ferry | Other (Income) Expense, Net                
Long Term Contracts Or Programs Disclosure [Line Items]                
Accrued deductible on insurance coverage     0.1          
Forty-Vehicle Ferry | Minimum                
Long Term Contracts Or Programs Disclosure [Line Items]                
Incremental forecast costs     1.0          
Forty-Vehicle Ferry | Maximum                
Long Term Contracts Or Programs Disclosure [Line Items]                
Incremental forecast costs     4.0          
Towing, Salvage and Rescue Ship                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins 6.7   $ 6.7          
Number of vehicle ferry projects | Vechicle     5          
Reserve for loss $ 3.1   $ 3.1          
Towing, Salvage and Rescue Ship | Minimum                
Long Term Contracts Or Programs Disclosure [Line Items]                
Projects, percent complete (percentage) 5.00%   5.00%          
Towing, Salvage and Rescue Ship | Maximum                
Long Term Contracts Or Programs Disclosure [Line Items]                
Projects, percent complete (percentage) 55.00%   55.00%          
Jacket and Deck                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins $ 0.6   $ 1.1          
Paddlewheel Riverboat and Subsea Components Projects                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins     $ 1.5          
Ice-Breaker Tug                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins   $ 0.5   $ 1.3        
Reserve for loss   0.1   0.1        
Subsea Components                
Long Term Contracts Or Programs Disclosure [Line Items]                
Change in estimated margins   1.5   1.4        
Reserve for loss   $ 0.6   $ 0.6        
Research Vessel Projects                
Long Term Contracts Or Programs Disclosure [Line Items]                
Number of Research Vessels Projects | Project     3          
Forecast | Harbor Tug                
Long Term Contracts Or Programs Disclosure [Line Items]                
Projects, percent complete (percentage)           90.00%    
Forecast | Forty-Vehicle Ferry                
Long Term Contracts Or Programs Disclosure [Line Items]                
Projects, percent complete (percentage)         75.00%