Quarterly report pursuant to Section 13 or 15(d)

Investments, At Equity, And Advances To 50% Or Less Owned Companies (Narrative) (Details)

v3.7.0.1
Investments, At Equity, And Advances To 50% Or Less Owned Companies (Narrative) (Details)
$ in Thousands
3 Months Ended 6 Months Ended
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
equipment
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Schedule Of Equity Method Investments [Line Items]          
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents   $ 5,900 $ 5,900    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables   (4,148) (4,148)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets   (61,626) (61,626)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable   (747) (747)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other   76 76    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt   41,186 41,186    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other   (43) (43)    
Noncontrolling interests in subsidiaries   17,834 17,834   $ 5,544
Guarantor Obligations, Maximum Exposure, Undiscounted   900 900    
Mexmar [Member]          
Schedule Of Equity Method Investments [Line Items]          
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital     $ 7,400    
Falcon Global [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     2    
Partners' Capital Account, Contributions     $ (400)    
Payments for Advance to Affiliate     2,000    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents   1,943 1,943    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets   785 785    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables   (291) (291)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets   (19,374) (19,374)    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment   96,000 96,000    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable   3,201 3,201    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other   1,153 1,153    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt   58,335 58,335    
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other   (1,000) (1,000)    
Noncontrolling interests in subsidiaries   17,374 17,374    
Long-term Debt   57,800 $ 57,800 $ 58,300  
Sea-Cat Crewzer II [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     2    
Payments to Acquire Businesses, Gross     $ 11,300    
Sea Cat Crewzer [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     2    
Payments to Acquire Businesses, Gross     $ 4,400    
OSV Partners [Member]          
Schedule Of Equity Method Investments [Line Items]          
Partners' Capital Account, Contributions   (1,800) (2,300)    
Long-term Debt   31,800 $ 31,800    
Other Offshore Marine Services Joint Ventures [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     8    
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital     $ 1,600    
Guarantor Obligations, Maximum Exposure, Undiscounted   $ 800 $ 800    
Allocable Share of Uncalled Capital       $ 1,800  
Offshore Support Vessels [Member] | Mexmar [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     15    
Offshore Support Vessels [Member] | OSV Partners [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     5    
Liftboats [Member] | Mexmar [Member]          
Schedule Of Equity Method Investments [Line Items]          
Number of Equipment Operated | equipment     2    
Subsequent Event [Member] | OSV Partners [Member]          
Schedule Of Equity Method Investments [Line Items]          
Partners' Capital Account, Contributions $ (500)