Leases (Narrative) (Details)	12 Months Ended
	Dec. 31, 2012
Minimum [Member] | Tank Barges [Member]
Operating Leased Assets [Line Items]
Lease agreements expiring terms	1 year
Minimum [Member] | Towing Vessels [Member]
Operating Leased Assets [Line Items]
Lease agreements expiring terms	30 days
Maximum [Member] | Tank Barges [Member]
Operating Leased Assets [Line Items]
Lease agreements expiring terms	10 years
Maximum [Member] | Towing Vessels [Member]
Operating Leased Assets [Line Items]
Lease agreements expiring terms	5 years