Annual report pursuant to Section 13 and 15(d)

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

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Organization and Summary of Significant Accounting Policies - Additional Information (Details)
12 Months Ended
Dec. 31, 2019
USD ($)
segment
vessel
ferry
tug
ship
towboat
Dec. 31, 2018
USD ($)
segment
Jan. 01, 2018
USD ($)
Significant Accounting Policies [Line Items]      
Number of operating segments | segment 3 4  
Number of corporate non-operating segments | segment 1 1  
Number of harbor tug vessels 4    
Number of regional class research vessels 3    
Number of ferries | ferry 3    
Number of ice-breaker tug vessels | tug 1    
Number of towing, salvage and rescue vessels | ship 3    
Number of OSVs 2    
Number of harbor tug vessels 6    
Number of towboats | towboat 2    
Prepaid contract costs | $ $ 0 $ 0  
Accounting Standards Update 2014-09      
Significant Accounting Policies [Line Items]      
Cumulative effect of new accounting principle in period of adoption | $     $ 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