Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013 Segment	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of operating segments		6
Revenues from External Customers [Abstract]
Fixed Revenue		$ 55,956	$ 28,758
Variable Revenue		25,168	36,446
Total Revenue from External Customers		81,124	65,204
Intersegment Revenues (Eliminated)		5,519	5,061
Intersegment Expenses (Eliminated)		(5,519)	(5,061)
Voyage Expenses		69,591	50,826
Loss (Income) of Unconsolidated Entities		270	70
Gross Voyage Profit (Loss)		11,263	14,308
Gross Voyage Profit Percentage (in hundredths)		14.00%	22.00%
Vessel and Other Depreciation		5,794	6,357
Gross Profit (Loss)		5,469	7,951
Interest Expense		2,201	2,727
Segment Profit (Loss)		3,268	5,224
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		3,268	5,224
Unallocated Amounts [Abstract]
Administrative and General Expenses		(5,433)	(5,508)
Gain on Sale of Other Assets	3,800	0	3,799
Derivative Gain		77	149
Gain on Sale of Investment		0	42
Other Income from Vessel Financing		555	622
Investment Income		40	128
Foreign Exchange Gain (Loss)		3,181	3,648
Provision for Income Taxes		(35)	(168)
Net Income		1,653	7,936
Jones Act [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		31,855	6,306
Variable Revenue		0	0
Total Revenue from External Customers		31,855	6,306
Intersegment Revenues (Eliminated)		0	0
Intersegment Expenses (Eliminated)		0	0
Voyage Expenses		25,556	6,753
Gross Voyage Profit (Loss)		6,299	(447)
Gross Voyage Profit Percentage (in hundredths)		20.00%	(7.00%)
Vessel and Other Depreciation		1,107	305
Gross Profit (Loss)		5,192	(752)
Interest Expense		341	52
Segment Profit (Loss)		4,851	(804)
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		4,851	(804)
Pure Car/Truck Carriers [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		16,395	20,015
Variable Revenue		11,477	12,587
Total Revenue from External Customers		27,872	32,602
Intersegment Revenues (Eliminated)		0	0
Intersegment Expenses (Eliminated)		0	0
Voyage Expenses		23,684	24,168
Gross Voyage Profit (Loss)		4,188	8,434
Gross Voyage Profit Percentage (in hundredths)		15.00%	26.00%
Vessel and Other Depreciation		2,039	3,473
Gross Profit (Loss)		2,149	4,961
Interest Expense		616	1,065
Segment Profit (Loss)		1,533	3,896
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		1,533	3,896
Dry Bulk Carriers [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		874	2,437
Variable Revenue		3,361	3,073
Total Revenue from External Customers		4,235	5,510
Intersegment Revenues (Eliminated)		0	0
Intersegment Expenses (Eliminated)		0	0
Voyage Expenses		5,203	4,267
Loss (Income) of Unconsolidated Entities		331	(42)
Gross Voyage Profit (Loss)		(1,299)	1,285
Gross Voyage Profit Percentage (in hundredths)		(31.00%)	23.00%
Vessel and Other Depreciation		1,638	1,363
Gross Profit (Loss)		(2,937)	(78)
Interest Expense		835	1,087
Segment Profit (Loss)		(3,772)	(1,165)
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		(3,772)	(1,165)
Rail Ferry [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		0	0
Variable Revenue		9,128	9,201
Total Revenue from External Customers		9,128	9,201
Intersegment Revenues (Eliminated)		0	0
Intersegment Expenses (Eliminated)		0	0
Voyage Expenses		7,671	8,440
Loss (Income) of Unconsolidated Entities		(61)	112
Gross Voyage Profit (Loss)		1,518	649
Gross Voyage Profit Percentage (in hundredths)		17.00%	7.00%
Vessel and Other Depreciation		495	698
Gross Profit (Loss)		1,023	(49)
Interest Expense		163	221
Segment Profit (Loss)		860	(270)
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		860	(270)
Specialty Contracts [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		6,832	0
Variable Revenue		855	11,298
Total Revenue from External Customers		7,687	11,298
Intersegment Revenues (Eliminated)		0	0
Intersegment Expenses (Eliminated)		0	0
Voyage Expenses		7,497	7,285
Gross Voyage Profit (Loss)		190	4,013
Gross Voyage Profit Percentage (in hundredths)		2.00%	36.00%
Vessel and Other Depreciation		515	516
Gross Profit (Loss)		(325)	3,497
Interest Expense		133	170
Segment Profit (Loss)		(458)	3,327
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		(458)	3,327
Other [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		0	0
Variable Revenue		347	287
Total Revenue from External Customers		347	287
Intersegment Revenues (Eliminated)		5,519	5,061
Intersegment Expenses (Eliminated)		(5,519)	(5,061)
Voyage Expenses		(20)	(87)
Gross Voyage Profit (Loss)		367	374
Gross Voyage Profit Percentage (in hundredths)		106.00%	130.00%
Vessel and Other Depreciation		0	2
Gross Profit (Loss)		367	372
Interest Expense		113	132
Segment Profit (Loss)		254	240
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		$ 254	$ 240