Operating Segments (Information About Segment Profit and Loss and Segment Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Fixed Revenue	$ 41,492	$ 51,281
Variable Revenue	12,309	16,745
Total Revenues	53,801	68,026
Voyage Expenses	43,077	52,211
Amortization Expenses	3,079	5,187
(Income) Loss of Unconsolidated Entities	142	893
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 7,787	$ 11,521
Gross Voyage Profit (Loss) Margin	14.00%	17.00%
Jones Act [Member]
Segment Reporting Information [Line Items]
Fixed Revenue	$ 22,746	$ 24,595
Total Revenues	22,746	24,595
Voyage Expenses	17,019	18,590
Amortization Expenses	2,216	3,828
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 3,511	$ 2,177
Gross Voyage Profit (Loss) Margin	15.00%	9.00%
PCTC [Member]
Segment Reporting Information [Line Items]
Fixed Revenue	$ 11,577	$ 14,247
Variable Revenue	4,981	7,533
Total Revenues	16,558	21,780
Voyage Expenses	14,131	17,020
Amortization Expenses	556	715
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 1,871	$ 4,045
Gross Voyage Profit (Loss) Margin	11.00%	19.00%
Dry Bulk Carriers [Member]
Segment Reporting Information [Line Items]
Fixed Revenue		$ 1,868
Variable Revenue		1,255
Total Revenues		3,123
Voyage Expenses		2,580
Amortization Expenses		61
(Income) Loss of Unconsolidated Entities		635
Gross Voyage Profit (Loss) (excluding Depreciation Expense)		$ 1,117
Gross Voyage Profit (Loss) Margin		36.00%
Rail-Ferry [Member]
Segment Reporting Information [Line Items]
Variable Revenue	$ 6,775	$ 7,534
Total Revenues	6,775	7,534
Voyage Expenses	5,428	6,635
Amortization Expenses	254	285
(Income) Loss of Unconsolidated Entities	142	(74)
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 1,235	$ 540
Gross Voyage Profit (Loss) Margin	18.00%	7.00%
Specialty Contracts [Member]
Segment Reporting Information [Line Items]
Fixed Revenue	$ 7,169	$ 10,571
Variable Revenue	439	185
Total Revenues	7,608	10,756
Voyage Expenses	6,423	7,557
Amortization Expenses	53	298
(Income) Loss of Unconsolidated Entities		332
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 1,132	$ 3,233
Gross Voyage Profit (Loss) Margin	15.00%	30.00%
Other [Member]
Segment Reporting Information [Line Items]
Variable Revenue	$ 114	$ 238
Total Revenues	114	238
Voyage Expenses	76	(171)
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 38	$ 409