Long Term Debt (Narrative) (Details) (USD $)	3 Months Ended			12 Months Ended	1 Months Ended
	Mar. 31, 2015 item	Dec. 31, 2014 item	Mar. 31, 2014	Dec. 31, 2014 item	Dec. 31, 2017	Sep. 30, 2015	Mar. 05, 2015 item	Sep. 24, 2013	Aug. 26, 2014	Aug. 31, 2014
Line of Credit Facility [Line Items]
Senior secured credit facility, current borrowing capacity	$ 95,000,000
Line of credit								50,000,000
Proceeds from borrowings of line of credit	5,000,000		8,000,000
Total principal due	226,043,000	242,888,000		242,888,000
Loss on Extinguishment of Debt	95,000
Number of loan facilities	2
Number of shipping companies	2
Amount of non-amortizing guarantee under second guarantee	1,000,000
Deferred gains from vessel purchase and refinancing transactions						11,300,000
Number of lenders who elected to adjust definition of EBITDA	2
Line of credit, increase	15,000,000
Number of lessors who agreed to defer the date when a more stringent leverage ratio and increased liquidity would be attained	2
Number of non-performing assets identified		5
Number of assets held for sale impairment was recorded on		1
Increase in valuation allowance	730,000
Number of held for sale assets sold prior to December 31, 2014				1
Number of held for sale assets sale was finalized for							1
Number of held for sale assets being actively marketed	3
Possible amount to refinance certain unencumbered assets	12,000,000
Possible amount of bank financing for construction and renovation of future corporate office	6,900,000
Incentives from the State of Louisiana	4,600,000
Incentives from the State of Louisiana expected to receive during 2015	600,000
Amount of remaining cost of building construction to be funded by cash on hand	6,900,000
Total amount paid off	2,500,000		8,000,000
Scenario, Forecast [Member]
Line of Credit Facility [Line Items]
Amount of non-amortizing guarantee under second guarantee					510,000
Loan Agreement [Member] | DVB Bank SE [Member]
Line of Credit Facility [Line Items]
Term loan facility principal amount									38,500,000
Loan Agreement [Member] | RBS Asset Finance [Member]
Line of Credit Facility [Line Items]
Term loan facility principal amount										23,000,000
Senior Secured Credit Facility [Member]
Line of Credit Facility [Line Items]
Term loan facility principal amount	45,000,000							45,000,000
Line of credit	50,000,000
Total principal due	41,000,000
Additional Term Loan [Member]
Line of Credit Facility [Line Items]
Proceeds from borrowings of line of credit	50,000,000
Standby Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit	20,000,000							20,000,000
Swingline Loans [Member]
Line of Credit Facility [Line Items]
Line of credit	5,000,000							5,000,000
Line Of Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	7,600,000
Line of Credit Facility, Remaining Borrowing Capacity	1,400,000
Consolidated Leverage Ratio	5.00%
Minimum fixed charge coverage ratio	1.05%
Minimum Liquidity Amount	20,000,000
Minimum Net Worth	228,000,000
Consolidated Net Income Earned	50.00%
Percent Of The Proceeds Of Issuances Of Equity Interests Received	100.00%
Future Consolidated Leverage Ratio through the fiscal quarter ending December 31, 2015	5.00%
Future Consolidated Leverage Ratio fiscal quarter ending March 31, 2016	4.75%
Future Consolidated Leverage Ratio beginning the quarter ending June 30, 2016 through the quarter ending September 30, 2016	4.50%
Future Consolidated Leverage Ratio after September 30, 2016	4.25%
Future Minimum Fixed Charge Coverage Ratio beginning with the quarter ending September 30, 2014 through the quarter ending December 31, 2014	1.10%
Future Minimum Fixed Charge Coverage Ratio beginning with the quarter ending March 31, 2015 through the quarter ending December 31, 2015	1.15%
Future Minimum Fixed Charge Coverage Ratio beginning with the quarter ending March 31, 2016 through the quarter ending June 30, 2016	1.20%
Future Minimum Fixed Charge Coverage Ratio after June 30, 2016	1.25%
Future fixed charge coverage ratio through fiscal year 2015	1.05%
Future fixed charge coverage ratio beginning with the quarter ending March 31, 2016	1.15%
Future fixed charge coverage ratio beginning with the quarter ending June 30, 2016 and for all periods thereafter	1.20%
Loan Facility A [Member]
Line of Credit Facility [Line Items]
Percentage of equity position	25.00%
Percentage of equity position guaranteed	5.00%
Amount of guarantee	3,600,000			3,600,000
Semi-annual reduction in guarantee through December 2018	165,000
Loan Facility B [Member]
Line of Credit Facility [Line Items]
Percentage of equity position	23.70%
Amount of non-amortizing guarantee	1,000,000
Amount of facility covered by overall bank guarantee	11,000,000
Handysize Vessel [Member]
Line of Credit Facility [Line Items]
Related debt paid off	$ 13,500,000