Equipment Acquisitions and Dispositions (Details) $ in Thousands		9 Months Ended
	Oct. 29, 2020 USD ($) vessel	Sep. 30, 2020 USD ($) equipment vessel	Sep. 30, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Payments to acquire property, plant and equipment		$ 16,326	$ 17,351
Sales Price of Equipment		9,600
Gain (Loss) on Disposition of Property Plant Equipment		8,200
Proceeds from other long-term financial liabilities		33,662	$ 0
Subsequent Event
Property, Plant and Equipment [Line Items]
Sales Price of Equipment	$ 1,800
Gain (Loss) on Disposition of Property Plant Equipment	$ 200
Gains on Asset Dispositions, Net
Property, Plant and Equipment [Line Items]
Amortization of Deferred Gains on Sale of Property		$ 1,000
U.S.-flag - Harbor Tugs
Property, Plant and Equipment [Line Items]
Number of equipment committed to purchase | equipment		4
Equipment Subject to Failed Sale Leaseback, Number of Units | equipment		3
U.S.-flag - Harbor Tugs | Minimum
Property, Plant and Equipment [Line Items]
Failed Sale Leaseback Transaction, Lease Terms		72
U.S.-flag - Harbor Tugs | Maximum
Property, Plant and Equipment [Line Items]
Failed Sale Leaseback Transaction, Lease Terms		84
Inland River Dry-Cargo Barges
Property, Plant and Equipment [Line Items]
Number of Equipment Disposed | vessel		39
Bulk carriers - U.S.-flag | Subsequent Event
Property, Plant and Equipment [Line Items]
Number of Equipment Disposed | vessel	1