Contingencies and Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013 Segment	Dec. 31, 2012 Segment
Certain Significant Risks and Uncertainties [Abstract]
Customer relationship period	40 years
Number of single customers accounting more than 10% of segment revenue	0	0	0
Percentage of customers revenue (in hundredths)	10.00%	10.00%	10.00%
Segment operates authorized distributors	17
Diesel engine services segment's relationship	49 years
Guarantor Obligations [Line Items]
Issued guaranties	$ 36,566,000
Guarantor Obligations, Term	All of these instruments have an expiration date within four years.
Performance Bonds [Member]
Guarantor Obligations [Line Items]
Issued guaranties	29,133,000
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Issued guaranties	7,433,000
Gulfco Marine Superfund Site [Member]
Site Contingency [Line Items]
Number of other companies also named as Potentially Responsible Parties ("PRPs")	3
Number of companies named as Potentially Responsible Parties ("PRPs")	4
EPA incurred cleanup expense	4,500,000
EPA oversight costs	1,800,000
Number of defendants seeking contribution and indemnity under CERCLA	21
Portland Harbor Superfund Site [Member]
Site Contingency [Line Items]
Number of other companies also named as Potentially Responsible Parties ("PRPs")	250
Number of spills	4
Palmer Barge Line Superfund Site [Member]
Site Contingency [Line Items]
Number of other companies also named as Potentially Responsible Parties ("PRPs")	45
Number of other companies also in an investigation and feasibility study agreement with EPA	3
Number of new companies in an agreement with the EPA	5
Number of Potentially Responsible Parties notified by EPA of intent to recover costs	30
EPA notification intent to recover costs incurred	$ 2,949,000
Marine Transportation's [Member]
Certain Significant Risks and Uncertainties [Abstract]
Percentage of inland revenue (in hundredths)	80.00%
Percentage of costal revenue (in hundredths)	85.00%
Number of single customers accounting more than 10% of segment revenue	0	0	0
Marine Transportation's [Member] | Minimum [Member]
Certain Significant Risks and Uncertainties [Abstract]
Range of renewal options under term contracts	1 year
Marine Transportation's [Member] | Maximum [Member]
Certain Significant Risks and Uncertainties [Abstract]
Range of renewal options under term contracts	5 years