Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Segment	Jun. 30, 2012
Segment Reporting Information [Line Items]
Number of operating segments				6
Revenues from External Customers [Abstract]
Fixed Revenue		$ 51,029	$ 33,431	$ 107,541	$ 73,014
Variable Revenue		23,868	26,889	48,480	52,510
Total Revenue from External Customers		74,897	60,320	156,021	125,524
Intersegment Revenues (Eliminated)		(5,519)	(5,250)	(11,038)	(10,311)
Intersegment Expenses (Eliminated)		5,519	5,250	11,038	10,311
Voyage Expenses		61,508	47,026	131,099	97,852
Loss (Income) of Unconsolidated Entities		75	(651)	345	(581)
Gross Voyage Profit		13,314	13,945	24,577	28,253
Gross Voyage Profit Percentage (in hundredths)		18.00%	23.00%	16.00%	23.00%
Vessel and Other Depreciation		5,815	5,723	11,609	12,080
Gross Profit (Loss)		7,499	8,222	12,968	16,173
Interest Expense		2,077	2,281	4,278	5,008
Segment Profit (Loss)		5,422	5,941	8,690	11,165
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		5,422	5,941	8,690	11,165
Unallocated Amounts [Abstract]
Administrative and General Expenses		(6,170)	(4,720)	(11,603)	(10,228)
Gain on Sale of Other Assets	3,800	0	667	0	4,466
Ineffective Portion on Derivative Instrument		205	(117)	282	32
Gain on Sale of Investment		0	24	0	66
Other Income from Vessel Financing		539	605	1,094	1,227
Investment Income		42	146	82	274
Foreign Exchange Gain/(Loss)		1,836	(1,734)	5,017	1,914
(Provisions) for Income Taxes		(15)	(108)	(50)	(276)
Net Income		1,859	704	3,512	8,640
Jones Act [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		27,725	5,522	59,579	12,553
Variable Revenue		0	726
Total Revenue from External Customers		27,725	6,248	59,579	12,553
Intersegment Expenses (Eliminated)		0	0	0	0
Voyage Expenses		22,204	5,094	47,694	12,010
Gross Voyage Profit		5,521	1,154	11,885	543
Gross Voyage Profit Percentage (in hundredths)		20.00%	18.00%	20.00%	4.00%
Vessel and Other Depreciation		1,156	305	2,263	610
Gross Profit (Loss)		4,365	849	9,622	(67)
Interest Expense		320	296	661	347
Segment Profit (Loss)		4,045	553	8,961	(414)
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		4,045	553	8,961	(414)
Pure Car/Truck Carriers [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		16,804	16,684	33,757	35,503
Variable Revenue		8,286	12,309	19,207	26,093
Total Revenue from External Customers		25,090	28,993	52,964	61,596
Intersegment Expenses (Eliminated)		0	0	0	0
Voyage Expenses		20,453	22,222	43,926	46,231
Gross Voyage Profit		4,637	6,771	9,038	15,365
Gross Voyage Profit Percentage (in hundredths)		18.00%	23.00%	17.00%	25.00%
Vessel and Other Depreciation		2,093	2,612	4,132	6,088
Gross Profit (Loss)		2,544	4,159	4,906	9,277
Interest Expense		579	782	1,196	1,847
Segment Profit (Loss)		1,965	3,377	3,710	7,430
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		1,965	3,377	3,710	7,430
Dry Bulk Carriers [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		665	2,431	1,538	4,869
Variable Revenue		4,188	4,160	7,549	7,233
Total Revenue from External Customers		4,853	6,591	9,087	12,102
Intersegment Expenses (Eliminated)		0	0	0	0
Voyage Expenses		4,473	4,294	9,674	8,561
Loss (Income) of Unconsolidated Entities		7	(618)	338	(660)
Gross Voyage Profit		373	2,915	(925)	4,201
Gross Voyage Profit Percentage (in hundredths)		8.00%	44.00%	(10.00%)	35.00%
Vessel and Other Depreciation		1,638	1,575	3,276	2,937
Gross Profit (Loss)		(1,265)	1,340	(4,201)	1,264
Interest Expense		796	819	1,631	1,907
Segment Profit (Loss)		(2,061)	521	(5,832)	(643)
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		(2,061)	521	(5,832)	(643)
Rail Ferry [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		0	0	0	0
Variable Revenue		9,523	9,396	18,697	18,597
Total Revenue from External Customers		9,523	9,396	18,697	18,597
Intersegment Expenses (Eliminated)		0	0	0	0
Voyage Expenses		7,762	7,948	15,482	16,388
Loss (Income) of Unconsolidated Entities		68	(33)	7	79
Gross Voyage Profit		1,693	1,481	3,208	2,130
Gross Voyage Profit Percentage (in hundredths)		18.00%	16.00%	17.00%	11.00%
Vessel and Other Depreciation		410	701	905	1,399
Gross Profit (Loss)		1,283	780	2,303	731
Interest Expense		154	161	317	382
Segment Profit (Loss)		1,129	619	1,986	349
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		1,129	619	1,986	349
Specialty Contracts [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		5,835	8,794	12,667	20,089
Variable Revenue		1,671	0	2,526
Total Revenue from External Customers		7,506	8,794	15,193	20,089
Intersegment Expenses (Eliminated)		0	0	0	0
Voyage Expenses		6,539	7,438	14,037	14,720
Gross Voyage Profit		967	1,356	1,156	5,369
Gross Voyage Profit Percentage (in hundredths)		13.00%	15.00%	8.00%	27.00%
Vessel and Other Depreciation		518	520	1,033	1,033
Gross Profit (Loss)		449	836	123	4,336
Interest Expense		124	125	256	295
Segment Profit (Loss)		325	711	(133)	4,041
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		325	711	(133)	4,041
Other [Member]
Revenues from External Customers [Abstract]
Fixed Revenue		0	0	0	0
Variable Revenue		200	298	501	587
Total Revenue from External Customers		200	298	501	587
Intersegment Revenues (Eliminated)		(5,519)	(5,250)	(11,038)	(10,311)
Intersegment Expenses (Eliminated)		5,519	5,250	11,038	10,311
Voyage Expenses		77	30	286	(58)
Gross Voyage Profit		123	268	215	645
Gross Voyage Profit Percentage (in hundredths)		62.00%	90.00%	43.00%	110.00%
Vessel and Other Depreciation		0	10	0	13
Gross Profit (Loss)		123	258	215	632
Interest Expense		104	98	217	230
Segment Profit (Loss)		19	160	(2)	402
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Segment Profit (Loss)		$ 19	$ 160	$ (2)	$ 402