Quarterly report pursuant to Section 13 or 15(d)

Organization and Summary of Significant Accounting Policies - Additional Information (Details)

v3.20.2
Organization and Summary of Significant Accounting Policies - Additional Information (Details)
 6 Months Ended 12 Months Ended
Jun. 30, 2020
USD ($)
segment
tug
vessel
ferry
ship
towboat
Dec. 31, 2019
USD ($)
segment
Significant Accounting Policies [Line Items]    
Number of operating segments | segment 2 3
Number of corporate non-operating segments | segment 1 1
Number of harbor tug 2  
Number of regional class research vessels | vessel 3  
Number of ferries | ferry 3  
Number of towing, salvage and rescue vessels | ship 5  
Number of OSVs | vessel 2  
Number of harbor tug 8  
Number of towboats | towboat 2  
Number of ice breaker tug 1  
Prepaid contract costs | $ $ 0 $ 0
Other (income) expense, net    
Significant Accounting Policies [Line Items]    
Gain on settlement of contract dispute for project completed in 2015 | $ $ 10,000,000.0  
Minimum    
Significant Accounting Policies [Line Items]    
Property, plant and equipment, useful life 3 years  
Maximum    
Significant Accounting Policies [Line Items]    
Property, plant and equipment, useful life 25 years