Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Nature Of Operations And Accounting Policies (Schedule Of Property And Equipment By Major Classes) (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Property, Plant and Equipment [Line Items]      
Historical cost $ 1,441,871 $ 1,442,382 $ 1,407,329
Accumulated depreciation (647,679) (624,024) (560,819)
Net property and equipment 794,192 818,358 846,510
Operating Segments | Ocean Services      
Property, Plant and Equipment [Line Items]      
Historical cost 928,950 932,267 930,230
Accumulated depreciation (407,286) (380,553) (341,999)
Net property and equipment 521,664 551,714 588,231
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 (294,182) (267,894)  
Net property and equipment 355,613 381,901  
Operating Segments | Ocean Services | Harbor Tugs - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 127,709    
Accumulated depreciation (51,681)    
Net property and equipment 76,028    
Operating Segments | Ocean Services | Harbor and Offshore Tugs - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost   133,419  
Accumulated depreciation   (47,637)  
Net property and equipment   85,782  
Operating Segments | Ocean Services | Harbor tugs - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 45,379 45,379  
Accumulated depreciation (18,313) (16,067)  
Net property and equipment 27,066 29,312  
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 (17,694) (16,171)  
Net property and equipment 21,544 23,067  
Operating Segments | Ocean Services | Short-sea container/RORO vessels - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 27,073 27,073  
Accumulated depreciation (14,121) (11,990)  
Net property and equipment 12,952 15,083  
Operating Segments | Ocean Services | Bulk carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Historical cost 6,300 13,000  
Accumulated depreciation (4,700) (9,800)  
Net property and equipment 1,600 3,200  
Operating Segments | Ocean Services | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 18,632 21,516  
Accumulated depreciation (6,595) (10,994)  
Net property and equipment 12,037 10,522  
Operating Segments | Ocean Services | Construction in progress      
Property, Plant and Equipment [Line Items]      
Historical cost 14,824 2,847  
Operating Segments | Inland Services      
Property, Plant and Equipment [Line Items]      
Historical cost 479,588 469,120 438,848
Accumulated depreciation (224,096) (216,296) (195,094)
Net property and equipment 255,492 252,824 243,754
Operating Segments | Inland Services | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 28,706 27,536  
Accumulated depreciation (9,335) (11,388)  
Net property and equipment 19,371 16,148  
Operating Segments | Inland Services | Construction in progress      
Property, Plant and Equipment [Line Items]      
Historical cost 4,944 7,736  
Operating Segments | Inland Services | Inland river dry-cargo barges      
Property, Plant and Equipment [Line Items]      
Historical cost 216,032 225,278  
Accumulated depreciation (120,825) (118,615)  
Net property and equipment 95,207 106,663  
Operating Segments | Inland Services | Inland river specialty barges      
Property, Plant and Equipment [Line Items]      
Historical cost 3,828 3,828  
Accumulated depreciation (2,783) (2,344)  
Net property and equipment 1,045 1,484  
Operating Segments | Inland Services | Inland river liquid tank barges      
Property, Plant and Equipment [Line Items]      
Historical cost 18,898 19,784  
Accumulated depreciation (4,087) (3,684)  
Net property and equipment 14,811 16,100  
Operating Segments | Inland Services | Inland river towboats      
Property, Plant and Equipment [Line Items]      
Historical cost 66,231 62,207  
Accumulated depreciation (7,329) (4,981)  
Net property and equipment 58,902 57,226  
Operating Segments | Inland Services | Inland river harbor boats      
Property, Plant and Equipment [Line Items]      
Historical cost 26,765 19,296  
Accumulated depreciation (10,762) (9,324)  
Net property and equipment 16,003 9,972  
Operating Segments | Inland Services | Launch support boats      
Property, Plant and Equipment [Line Items]      
Historical cost 5,920    
Accumulated depreciation (178)    
Net property and equipment 5,742    
Operating Segments | Inland Services | Terminal and fleeting facilities      
Property, Plant and Equipment [Line Items]      
Historical cost 108,264 103,455  
Accumulated depreciation (68,797) (65,960)  
Net property and equipment 39,467 37,495  
Operating Segments | Witt O'Brien's LLC      
Property, Plant and Equipment [Line Items]      
Historical cost 493 1,134 1,227
Accumulated depreciation (442) (993) (1,031)
Net property and equipment 51 141 196
Operating Segments | Witt O'Brien's LLC | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 493 1,134  
Accumulated depreciation (442) (993)  
Net property and equipment 51 141  
Operating Segments | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 12,139 8,897 6,892
Accumulated depreciation (4,535) (2,450) (490)
Net property and equipment 7,604 6,447 6,402
Operating Segments | Other | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 12,139 8,897  
Accumulated depreciation (4,535) (2,450)  
Net property and equipment 7,604 6,447  
Corporate And Eliminations      
Property, Plant and Equipment [Line Items]      
Historical cost 20,701 30,964 30,132
Accumulated depreciation (11,320) (23,732) (22,205)
Net property and equipment 9,381 7,232 $ 7,927
Corporate And Eliminations | Other      
Property, Plant and Equipment [Line Items]      
Historical cost 20,701 30,964  
Accumulated depreciation (11,320) (23,732)  
Net property and equipment $ 9,381 $ 7,232