Annual report pursuant to Section 13 and 15(d)

Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Details Textual)

v3.19.1
Note 4 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Details Textual)
3 Months Ended 12 Months Ended
Dec. 28, 2018
USD ($)
Dec. 20, 2018
USD ($)
Sep. 28, 2018
USD ($)
Sep. 13, 2018
USD ($)
Jan. 17, 2018
USD ($)
Apr. 28, 2017
USD ($)
Sep. 30, 2018
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Equity Method Investment, Unrealized Intercompany Profit (Loss) Not Eliminated, Amount                 $ 28,500,000 $ 46,100,000  
Proceeds from Equity Method Investment, Distribution, Return of Capital                 $ 16,263,000 $ 40,000
Number of Equipment Acquired                 8 [1] 11 17
Payments to Acquire Property, Plant, and Equipment, Total                 $ 51,980,000 $ 69,021,000 $ 100,884,000
Unrecorded Unconditional Purchase Obligation, Total                 78,178,000    
Proceeds from Divestiture of Interest in Joint Venture                 8,017,000
Equity Method Investment, Other than Temporary Impairment                 1,200,000 8,800,000 6,900,000
Income (Loss) from Equity Method Investments, Total                 (3,415,000) 4,077,000 (6,314,000)
Equity Method Investments                 121,773,000 92,169,000  
Repayment of Notes Receivable from Related Parties                 116,000
MEXMAR Offshore [Member]                      
Partners' Capital Account, Contributions   $ 10,000,000                  
Noncontrolling Interest, Ownership Percentage by Parent   49.00%                  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners   51.00%                  
Offshore Vessel Holdings [Member]                      
Noncontrolling Interest, Ownership Percentage by Parent 49.00%                    
Payments to Acquire Interest in Joint Venture $ 4,900,000                    
Offshore Support Vessels, Supply [Member]                      
Number of Equipment Operated   11                  
ROV Support Vessels [Member]                      
Number of Equipment Operated   2                  
Offshore Terminal Vessel [Member]                      
Number of Equipment Operated   1                  
MexMar [Member]                      
Proceeds from Equity Method Investment, Distribution, Return of Capital                 9,800,000 7,400,000  
Partners' Capital Account, Contributions                     $ 7,400,000
Number of Equipment Acquired                     2
Payments to Acquire Machinery and Equipment                     $ 34,000,000
Revenue from Related Parties                 $ 300,000 300,000 300,000
Related Party Transaction, Expenses from Transactions with Related Party                     5,100,000
Equity Method Investment, Ownership Percentage                 49.00%    
Income (Loss) from Equity Method Investments, Total                 $ 2,736,000 10,103,000 3,556,000
Equity Method Investments                 $ 53,840,000 60,980,000  
MexMar [Member] | Offshore Support Vessels [Member]                      
Number of Equipment Operated                 16    
SeaCosco Offshore LLC [Member]                      
Number of Equipment Operated         8            
Partners' Capital Account, Contributions                 $ 29,600,000    
Payments to Acquire Property, Plant, and Equipment, Total         $ 163,300,000            
Equity Method Investment, Ownership Percentage         50.00%       50.00%    
Unrecorded Unconditional Purchase Obligation, Total                 $ 2,000,000    
Equity Method Investments                 28,002,000  
OSV Partners [Member]                      
Partners' Capital Account, Contributions                   2,300,000 1,200,000
Revenue from Related Parties                 $ 600,000 600,000 500,000
Equity Method Investment, Ownership Percentage                 30.40%    
Investment in Affiliates, Amount of Preferred Equity Offereing Participated     $ 5,000,000                
Payments to Acquire Interest in Subsidiaries and Affiliates, Total     1,100,000                
Commitment to Invest Additional Funds if Call By General Partner     1,100,000                
Payments to Acquire Loans Receivable     2,100,000                
Equity Method Investments                 $ 11,087,000 10,006,000  
OSV Partners [Member] | General Partner [Member]                      
Partners' Capital Account, Contributions     $ 5,000,000             6,000,000  
Equity Method Investment, Ownership Percentage                 38.60%    
OSV Partners [Member] | Offshore Support Vessels [Member]                      
Number of Equipment Operated                 5    
SEACOR Marlin LLC [Member]                      
Equity Method Investment, Ownership Percentage                 49.00%    
Equity Method Investment, Ownership, Percent Sold       51.00%         51.00%    
Proceeds from Divestiture of Interest in Joint Venture       $ 8,000,000              
Gain (Loss) on Disposition of Business       $ 400,000              
Equity Method Investments                 $ 7,579,000  
MEXMAR Offshore [Member]                      
Number of Equipment Operated   14                  
Equity Method Investment, Ownership Percentage                 49.00%    
Equity Method Investments                 $ 4,900,000  
MEXMAR Offshore [Member] | BRAZIL                      
Number of Equipment Operated   12                  
MEXMAR Offshore [Member] | UNITED KINGDOM                      
Number of Equipment Operated   2                  
Dynamic Offshore [Member]                      
Equity Method Investment, Ownership Percentage                 19.00%    
Equity Method Investment, Other than Temporary Impairment                   8,300,000  
Income (Loss) from Equity Method Investments, Total                 $ (2,700,000)    
Equity Method Investments                 $ 2,263,000 4,958,000  
Nautical Power [Member]                      
Equity Method Investment, Ownership Percentage                 50.00%    
Proceeds from Divestiture of Interest in Joint Venture             $ 6,400,000        
Equity Method Investments                 6,408,000  
Falcon Global [Member]                      
Partners' Capital Account, Contributions               $ 400,000      
Payments for Advance to Affiliate               $ 2      
Business Acquisition, Percentage of Voting Interests Acquired               100.00%      
Falcon Global [Member] | Liftboats [Member]                      
Number of Equipment Operated                 2    
Sea-Cat Crewzer II [Member]                      
Number of Equipment Operated           2     2    
Equity Method Investment, Ownership Percentage           50.00%          
Business Acquisition, Percentage of Voting Interests Acquired           100.00%          
Payments to Acquire Businesses, Gross           $ 11,300,000          
Sea-Cat Crewzer [Member]                      
Number of Equipment Operated           2     2    
Equity Method Investment, Ownership Percentage           50.00%          
Business Acquisition, Percentage of Voting Interests Acquired           100.00%          
Payments to Acquire Businesses, Gross           $ 4,400,000          
Other Offshore Marine Services Joint Ventures [Member]                      
Number of Equipment Operated                 8    
Proceeds from Equity Method Investment, Distribution, Return of Capital                 $ 1,700,000 2,600,000 800,000
Partners' Capital Account, Contributions                   800,000 500,000
Revenue from Related Parties                 300,000 700,000 800,000
Equity Method Investment, Other than Temporary Impairment                 1,200,000 500,000 500,000
Income (Loss) from Equity Method Investments, Total                 (6,151,000) (6,026,000) (9,870,000)
Equity Method Investments                 9,202,000 9,817,000  
Repayment of Notes Receivable from Related Parties                   $ 200,000  
Allocable Share of Uncalled Capital                 800,000    
Guarantee of Outstanding Charter Receivables                 $ 300,000    
Other Offshore Marine Services Joint Ventures [Member] | Offshore Support Vessels [Member]                      
Asset Impairment Charges, Total                     $ 2,700,000
[1] Excludes two AHTS vessels purchased from Managed Entity Seacor 88 and Seacor 888, and one crew transfer vessel purchased from the Company's joint venture FRS Windcat Offshore Logistics.