Basis of Presentation and Accounting Policies - Property and Equipment (Details) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($) equipment
Property, Plant and Equipment [Line Items]
Construction in progress	$ 16.4
Capitalized interest	$ 0.2
Petroleum and chemical carriers - U.S.-flag
Property, Plant and Equipment [Line Items]
Useful life	25 years
Bulk carriers - U.S.-flag
Property, Plant and Equipment [Line Items]
Useful life	25 years
Harbor and offshore tugs
Property, Plant and Equipment [Line Items]
Useful life	25 years
Ocean liquid tank barges
Property, Plant and Equipment [Line Items]
Useful life	25 years
Short-sea container/RORO vessels
Property, Plant and Equipment [Line Items]
Useful life	20 years
Inland river dry-cargo and specialty barges
Property, Plant and Equipment [Line Items]
Useful life	20 years
Inland river liquid tank barges
Property, Plant and Equipment [Line Items]
Useful life	25 years
Inland river towboats and harbor boats
Property, Plant and Equipment [Line Items]
Useful life	25 years
Terminal and fleeting facilities
Property, Plant and Equipment [Line Items]
Useful life	20 years
U.S.-flag - Harbor Tugs
Property, Plant and Equipment [Line Items]
Number of equipment committed to purchase \| equipment	4

Number Of Equipment Committed to Purchase

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- Definition

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

+ Details

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- Definition

Amount of interest capitalized during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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