| Summarized Segment Financial Information | Summarized financial information for our segments as of and for the three-year period ended December 31, 2020, is as follows (in thousands): 
|   |   | Year Ended December 31, 2020 |   |  
|   |   | Shipyard |   |   | F&S |   |   | Corporate |   |   | Total |   |  
| Revenue |   | $ | 153,698 |   |   | $ | 99,485 |   |   | $ | (2,224 | ) |   | $ | 250,959 |   |  
| Gross profit (loss) (1) |   |   | (19,274 | ) |   |   | 1,523 |   |   |   | — |   |   |   | (17,751 | ) |  
| Operating income (loss) (1) |   |   | (24,343 | ) |   |   | 5,893 |   |   |   | (8,709 | ) |   |   | (27,159 | ) |  
| Depreciation and amortization expense |   |   | 3,254 |   |   |   | 5,061 |   |   |   | 302 |   |   |   | 8,617 |   |  
| Capital expenditures |   |   | 6,499 |   |   |   | 4,522 |   |   |   | 191 |   |   |   | 11,212 |   |  
| Total assets (4) |   |   | 121,992 |   |   |   | 54,966 |   |   |   | 54,385 |   |   |   | 231,343 |   |    
|   |   | Year Ended December 31, 2019 |   |  
|   |   | Shipyard (5) |   |   | F&S (5) |   |   | Corporate |   |   | Total |   |  
| Revenue |   | $ | 168,466 |   |   | $ | 137,169 |   |   | $ | (2,327 | ) |   | $ | 303,308 |   |  
| Gross loss (2) |   |   | (16,025 | ) |   |   | (657 | ) |   |   | (317 | ) |   |   | (16,999 | ) |  
| Operating loss (2) |   |   | (26,428 | ) |   |   | (13,696 | ) |   |   | (9,897 | ) |   |   | (50,021 | ) |  
| Depreciation and amortization expense |   |   | 4,167 |   |   |   | 4,984 |   |   |   | 413 |   |   |   | 9,564 |   |  
| Capital expenditures |   |   | 1,827 |   |   |   | 1,963 |   |   |   | — |   |   |   | 3,790 |   |  
| Total assets (4) |   |   | 103,409 |   |   |   | 77,402 |   |   |   | 71,966 |   |   |   | 252,777 |   |    
|   |   | Year Ended December 31, 2018 |   |  
|   |   | Shipyard |   |   | F&S |   |   | Corporate |   |   | Total |   |  
| Revenue |   | $ | 96,424 |   |   | $ | 126,695 |   |   | $ | (1,872 | ) |   | $ | 221,247 |   |  
| Gross profit (loss) (3) |   |   | (10,472 | ) |   |   | 4,607 |   |   |   | (1,331 | ) |   |   | (7,196 | ) |  
| Operating income (loss) (3) |   |   | (14,396 | ) |   |   | 4,558 |   |   |   | (9,827 | ) |   |   | (19,665 | ) |  
| Depreciation and amortization expense |   |   | 4,229 |   |   |   | 5,826 |   |   |   | 295 |   |   |   | 10,350 |   |  
| Capital expenditures |   |   | 2,003 |   |   |   | 1,460 |   |   |   | 18 |   |   |   | 3,481 |   |  
| Total assets (4) |   |   | 97,197 |   |   |   | 102,719 |   |   |   | 58,374 |   |   |   | 258,290 |   |    
|   | (1) | Gross profit (loss) and operating income (loss) for 2020 includes project charges of $16.6 million for our Shipyard Division and project improvements of $2.7 million for our F&S Division.  Operating income (loss) also includes impairment charges and net losses on the sales of assets held for sale of $1.6 million and $2.5 million for our Shipyard Division and F&S Division, respectively, charges of $1.3 million associated with damage caused by Hurricane Laura at our Lake Charles Yard for our Shipyard Division, and a gain of $10.0 million associated with the settlement of a contract dispute for our F&S Division.  See Note 2 for further discussion of our project and hurricane impacts and Note 3 for further discussion of our facility closures and impairments.  |  
|   | (2) | Gross loss and operating loss for 2019 includes project charges of $12.3 million and $4.9 million for our Shipyard Division and F&S Division, respectively.  Operating loss also includes impairment charges and net gains on the sales of assets held for sale of $7.9 million and $8.9 million for our Shipyard Division and F&S Division, respectively, and restructuring costs of $0.7 million for our Corporate Division. See Note 2 for further discussion of our project impacts and Note 3 for further discussion of our impairments.  |  
|   | (3)  | Gross profit (loss) and operating income (loss) for 2018 includes project charges of $6.7 million and $2.4 million for our Shipyard Division and F&S Division, respectively.  Operating income (loss) also includes impairment charges of $1.0 million for our Shipyard Division and a net benefit of $7.8 million for our F&S Division, primarily related to a gain on the sale of our South Texas Properties of $7.7 million and a gain on insurance recoveries of $3.6 million, offset partially by impairments of $3.5 million. See Note 2 for further discussion of our project impacts and Note 3 for further discussion of our asset impairments.  |  
|   | (4) | Cash and short-term investments are reported within our Corporate Division.  |  
|   | (5) | Revenue of $9.2 million and gross loss and operating loss of $5.1 million for 2019, and contract assets and contract receivables of $6.0 million as of December 31, 2019, associated with our two forty-vehicle ferry projects were reclassified from our former Fabrication Division to our Shipyard Division to conform to the presentation of these projects for 2020.  |  |