Annual report pursuant to Section 13 and 15(d)

Nature Of Operations And Accounting Policies (Schedule Of Property And Equipment By Major Classes) (Details)

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Nature Of Operations And Accounting Policies (Schedule Of Property And Equipment By Major Classes) (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]      
Historical cost $ 1,442,382 $ 1,407,329 $ 1,380,469
Accumulated depreciation (624,024) (560,819) (502,544)
Net property and equipment 818,358 846,510 877,925
Operating Segments | Ocean Services      
Property, Plant and Equipment [Line Items]      
Historical cost 932,267 930,230 901,076
Accumulated depreciation (380,553) (341,999) (299,528)
Net property and equipment 551,714 588,231 601,548
Operating Segments | Ocean Services | Petroleum and chemical carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 649,795 649,795  
Accumulated depreciation (267,894) (241,604)  
Net property and equipment 381,901 408,191  
Operating Segments | Ocean Services | Harbor and offshore tugs - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 133,419 132,697  
Accumulated depreciation (47,637) (41,764)  
Net property and equipment 85,782 90,933  
Operating Segments | Ocean Services | Harbor tugs - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 45,379 45,379  
Accumulated depreciation (16,067) (13,822)  
Net property and equipment 29,312 31,557  
Operating Segments | Ocean Services | Ocean liquid tank barges - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 39,238 39,238  
Accumulated depreciation (16,171) (14,649)  
Net property and equipment 23,067 24,589  
Operating Segments | Ocean Services | Short-sea container/RORO vessels - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 27,073 29,846  
Accumulated depreciation (11,990) (10,644)  
Net property and equipment 15,083 19,202  
Operating Segments | Ocean Services | Bulk carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 13,000 13,000  
Accumulated depreciation (9,800) (9,800)  
Net property and equipment 3,200 3,200  
Operating Segments | Ocean Services | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 21,516 20,073  
Accumulated depreciation (10,994) (9,716)  
Net property and equipment 10,522 10,357  
Operating Segments | Ocean Services | Construction in progress      
Property, Plant and Equipment [Line Items]      
Historical cost 2,847 202  
Operating Segments | Inland Services      
Property, Plant and Equipment [Line Items]      
Historical cost 469,120 438,848 448,035
Accumulated depreciation (216,296) (195,094) (181,573)
Net property and equipment 252,824 243,754 266,462
Operating Segments | Inland Services | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 27,536 22,213  
Accumulated depreciation (11,388) (10,364)  
Net property and equipment 16,148 11,849  
Operating Segments | Inland Services | Construction in progress      
Property, Plant and Equipment [Line Items]      
Historical cost 7,736 7,868  
Operating Segments | Inland Services | Inland river dry-cargo barges      
Property, Plant and Equipment [Line Items]      
Historical cost 225,278 222,539  
Accumulated depreciation (118,615) (106,157)  
Net property and equipment 106,663 116,382  
Operating Segments | Inland Services | Inland river specialty barges      
Property, Plant and Equipment [Line Items]      
Historical cost 3,828 3,828  
Accumulated depreciation (2,344) (1,904)  
Net property and equipment 1,484 1,924  
Operating Segments | Inland Services | Inland river liquid tank barges      
Property, Plant and Equipment [Line Items]      
Historical cost 19,784 20,011  
Accumulated depreciation (3,684) (3,054)  
Net property and equipment 16,100 16,957  
Operating Segments | Inland Services | Inland river towboats      
Property, Plant and Equipment [Line Items]      
Historical cost 62,207 43,998  
Accumulated depreciation (4,981) (3,294)  
Net property and equipment 57,226 40,704  
Operating Segments | Inland Services | Inland river harbor boats      
Property, Plant and Equipment [Line Items]      
Historical cost 19,296 18,695  
Accumulated depreciation (9,324) (8,047)  
Net property and equipment 9,972 10,648  
Operating Segments | Inland Services | Terminal and fleeting facilities      
Property, Plant and Equipment [Line Items]      
Historical cost 103,455 99,696  
Accumulated depreciation (65,960) (62,274)  
Net property and equipment 37,495 37,422  
Operating Segments | Witt O'Brien's LLC      
Property, Plant and Equipment [Line Items]      
Historical cost 1,134 1,227 1,227
Accumulated depreciation (993) (1,031) (938)
Net property and equipment 141 196 289
Operating Segments | Witt O'Brien's LLC | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 1,134 1,227  
Accumulated depreciation (993) (1,031)  
Net property and equipment 141 196  
Operating Segments | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 8,897 6,892 0
Accumulated depreciation (2,450) (490) 0
Net property and equipment 6,447 6,402 0
Operating Segments | Other | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 8,897 6,892  
Accumulated depreciation (2,450) (490)  
Net property and equipment 6,447 6,402  
Corporate And Eliminations      
Property, Plant and Equipment [Line Items]      
Historical cost 30,964 30,132 30,131
Accumulated depreciation (23,732) (22,205) (20,505)
Net property and equipment 7,232 7,927 $ 9,626
Corporate And Eliminations | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 30,964 30,132  
Accumulated depreciation (23,732) (22,205)  
Net property and equipment $ 7,232 $ 7,927