Commitments And Contingencies (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) item	Sep. 30, 2015 USD ($)	Jan. 06, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 26, 2014 USD ($) item
Commitments And Contingencies [Line Items]
Number of vessels owned with commitments | item	21
Possible loss value if forced to acquire back vessels	$ 292,000
Reserves for lawsuit claims	292,000			$ 352,000
Insurance policies with deductibles, minimum amount per claim	1,500
Insurance policies with deductibles, maximum amount per claim	25,000
If Defaulted on any of Operating Lease Agreements [Member]
Commitments And Contingencies [Line Items]
Stipulated loss value if forced to buy back vessels	$ 73,500,000
Upon Notification of Bankruptcy by Ship Builder [Member]
Commitments And Contingencies [Line Items]
Deposit and interest collected			$ 4,200,000
Deposit reclassified to current receivable		$ 3,900,000
Interest accrued on receivable from customer		$ 300,000
Relocation of Corporate Headquarters to New Orleans [Member]
Commitments And Contingencies [Line Items]
Number of incentives from the State of Louisiana | item	2
Jones Act [Member] | Molten Sulphur Carrier [Member]
Commitments And Contingencies [Line Items]
Number of vessels held under operating lease contracts | item	3
Pure Car Truck Carriers [Member] | Pure Car Truck Carriers [Member]
Commitments And Contingencies [Line Items]
Number of vessels held under operating lease contracts | item	2
U.S. Customs And Border Protection [Member]
Commitments And Contingencies [Line Items]
Number of affiliates that allegedly failed to properly report the importation of spare parts consumed by vessels | item					2
Amount of proposed duty					$ 1,400,000
Amount of proposed penalty on assessment					$ 5,700,000
Louisiana [Member] | Relocation of Corporate Headquarters to New Orleans [Member]
Commitments And Contingencies [Line Items]
Incentive received	$ 10,300,000
Louisiana [Member] | Construction and Other Relocation Expenses [Member]
Commitments And Contingencies [Line Items]
Incentive received	$ 6,500,000