Operating Leases (Details)		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020 equipment
Petroleum and Chemical Carriers - U.S.-flag
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		2
Petroleum and Chemical Carriers - U.S.-flag | Minimum
Operating Leases [Line Items]
Sale Leaseback Transaction, Lease Terms	24
Petroleum and Chemical Carriers - U.S.-flag | Maximum
Operating Leases [Line Items]
Sale Leaseback Transaction, Lease Terms	71
U.S.-flag - Harbor Tugs
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		4
U.S.-flag Offshore Tug
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		1
Pure Car/Truck Carriers - U.S.-flag
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		4
Inland River Dry-Cargo Barges
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		50
Inland River Towboats
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		4
Inland River Harbor Boats
Operating Leases [Line Items]
Equipment Subject to Operating Lease, Number of Units		6
Other Equipment | Minimum
Operating Leases [Line Items]
Lessee, Operating Lease, Term of Contract	1 month	1 month
Other Equipment | Maximum
Operating Leases [Line Items]
Lessee, Operating Lease, Term of Contract	186 months	186 months