Annual report pursuant to Section 13 and 15(d)

Nature Of Operations And Accounting Policies (Narrative) (Details)

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Nature Of Operations And Accounting Policies (Narrative) (Details) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Jul. 03, 2017
Nature of Operations and Accounting Policies [Line Items]        
Proceeds from Issuance of Secured Debt   $ 8,000,000 $ 1,700,000  
Investment Owned, at Cost $ 4,300,000 4,300,000    
Depreciation 72,100,000 60,200,000 58,100,000  
Capitalized interest 2,700,000 11,500,000 14,100,000  
Amortization expense 2,931,000 2,414,000 $ 2,200,000  
Asset Impairment Charges $ (400,000) (1,100,000)    
Impairment of Intangible Assets, Finite-lived   $ (9,958,000)    
Shipping Services [Member]        
Nature of Operations and Accounting Policies [Line Items]        
Percentage of Operating Revenues 61.00% 52.00% 44.00%  
Inland River Services [Member]        
Nature of Operations and Accounting Policies [Line Items]        
Percentage of Operating Revenues 30.00% 38.00% 44.00%  
Witt O'Brien's LLC [Member]        
Nature of Operations and Accounting Policies [Line Items]        
Percentage of Operating Revenues 9.00% 10.00% 10.00%  
Goodwill, Impairment Loss   $ 19,600,000    
Dorian LPG [Member]        
Nature of Operations and Accounting Policies [Line Items]        
Investment Owned, Balance, Shares 5,200,000      
Investment Owned, at Fair Value $ 8.22 8.21    
Investment Owned, at Cost 13.66      
SCFCo Holdings        
Nature of Operations and Accounting Policies [Line Items]        
Asset Impairment Charges     $ (21,500,000)  
Equity Method Investment, Other than Temporary Impairment   $ 7,700,000 $ 21,500,000  
Illinois Corn Processing Llc [Member]        
Nature of Operations and Accounting Policies [Line Items]        
Noncontrolling Interest, Ownership Percentage by Parent       70.00%
Proceeds from Divestiture of Businesses 21,000,000      
Proceeds from Issuance of Secured Debt 32,800,000      
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax $ 10,900,000