Quarterly report pursuant to Section 13 or 15(d)

Investments, at Equity, and Advances to 50% or Less Owned Companies - Additional Information (Details)

v3.19.1
Investments, at Equity, and Advances to 50% or Less Owned Companies - Additional Information (Details)
3 Months Ended 12 Months Ended
Feb. 13, 2019
USD ($)
Dec. 28, 2018
USD ($)
Mar. 31, 2019
USD ($)
Vessel
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Vessel
Schedule Of Investments [Line Items]          
Payments to acquire interest in unconsolidated joint venture     $ 1,951,000 $ 19,950,000  
Amount guaranteed under arrangement     $ 36,600,000    
FRS Windcat Offshore Logistics GmbH          
Schedule Of Investments [Line Items]          
Number of equipment sold | Vessel     1    
Sale of vessel, consideration     $ 4,300,000    
SeaCosco Offshore LLC          
Schedule Of Investments [Line Items]          
Equity method investment, ownership percentage     50.00%    
Contributed capital     $ 2,000,000   $ 29,600,000
SeaCosco Offshore LLC | Platform Supply Vessels          
Schedule Of Investments [Line Items]          
Number of vessels delivered to the company | Vessel     2   2
Number of vessels for which the company gets title | Vessel     1   5
Offshore Vessel Holdings          
Schedule Of Investments [Line Items]          
Equity method investment, ownership percentage   49.00%      
Payments to acquire interest in unconsolidated joint venture   $ 4,900,000      
Offshore Vessel Holdings | Operadora Productora Y Exploradora Mexicana, and Affiliate of MexMar          
Schedule Of Investments [Line Items]          
Loans receivable, amount $ 10,000        
Loan receivable, repayment period 3 years        
Loans receiable, interest rate 15.00%        
Other Offshore Marine Services Joint Ventures          
Schedule Of Investments [Line Items]          
Equity method investment, ownership percentage     50.00%    
Amount guaranteed under arrangement     $ 3,000,000    
Allocable share of uncalled capital     $ 800,000