Quarterly report pursuant to Section 13 or 15(d)

Note 3 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Details Textual)

v3.10.0.1
Note 3 - Investments, at Equity, and Advances to 50% or Less Owned Companies (Details Textual)
$ in Thousands
6 Months Ended
Jan. 17, 2018
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Payments to Acquire Property, Plant, and Equipment, Total   $ 15,548 $ 28,803
Unrecorded Unconditional Purchase Obligation, Total   43,300  
Equity Method Investment, Other than Temporary Impairment   1,200  
Guarantor Obligations, Maximum Exposure, Undiscounted   51,600  
Grant DIS [Member]      
Capital Call   400  
SeaCosco Offshore LLC [Member]      
Number of Equipment Operated 8    
Payments to Acquire Property, Plant, and Equipment, Total $ 161,100    
Unrecorded Unconditional Purchase Obligation, Total $ 27,500 27,500  
Equity Method Investment, Ownership Percentage 50.00%    
Partners' Capital Account, Contributions   25,600  
SEACOR Holdings [Member]      
Equity Method Investment, Other than Temporary Impairment   1,200  
Equity Method Investments   $ 0  
Other Offshore Marine Services Joint Ventures [Member]      
Equity Method Investment, Ownership Percentage   50.00%  
Guarantor Obligations, Maximum Exposure, Undiscounted   $ 500  
Allocable Share of Uncalled Capital   $ 1,200