Significant Operations (Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Segment Profit and Loss [Abstract]
Revenues	$ 259,474	$ 294,834
Voyage Expenses	207,581	223,040
Amortization Expense	16,198	22,107
(Income) Loss of Unconsolidated Entities	4,049	(10)
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 31,646	$ 49,697
Gross Voyage Profit (Loss) Margin	12.00%	17.00%
Segment Assets	$ 297,865	$ 544,890
Expenditures for Segment Assets	37,060	79,701
Operating Segments [Member] \| Jones Act [Member]
Segment Profit and Loss [Abstract]
Revenues	86,898	124,854
Voyage Expenses	73,373	82,913
Amortization Expense	12,269	15,813
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 1,256	$ 26,128
Gross Voyage Profit (Loss) Margin	1.00%	21.00%
Segment Assets	$ 86,653	$ 141,705
Expenditures for Segment Assets	17,288	9,528
Operating Segments [Member] \| PCTC [Member]
Segment Profit and Loss [Abstract]
Revenues	83,283	78,081
Voyage Expenses	65,078	65,696
Amortization Expense	2,606	2,606
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 15,599	$ 9,779
Gross Voyage Profit (Loss) Margin	19.00%	13.00%
Segment Assets	$ 82,756	$ 160,020
Expenditures for Segment Assets	3,589	62,155
Operating Segments [Member] \| Dry Bulk Carriers [Member]
Segment Profit and Loss [Abstract]
Revenues	13,208	18,045
Voyage Expenses	9,439	13,327
Amortization Expense	201	236
(Income) Loss of Unconsolidated Entities	4,770	468
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ (1,202)	$ 4,014
Gross Voyage Profit (Loss) Margin	(9.00%)	22.00%
Segment Assets	$ 34,731	$ 134,729
Expenditures for Segment Assets		1,949
Operating Segments [Member] \| Rail-Ferry Service [Member]
Segment Profit and Loss [Abstract]
Revenues	34,005	34,577
Voyage Expenses	26,459	28,743
Amortization Expense	909	994
(Income) Loss of Unconsolidated Entities	393	193
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 6,244	$ 4,647
Gross Voyage Profit (Loss) Margin	18.00%	13.00%
Segment Assets	$ 46,758	$ 48,449
Expenditures for Segment Assets	3,921	363
Operating Segments [Member] \| Specialty Contracts [Member]
Segment Profit and Loss [Abstract]
Revenues	41,827	39,765
Voyage Expenses	33,871	33,973
Amortization Expense	213	2,433
(Income) Loss of Unconsolidated Entities	(1,114)	(671)
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	$ 8,857	$ 4,030
Gross Voyage Profit (Loss) Margin	21.00%	10.00%
Segment Assets	$ 39,731	$ 57,267
Expenditures for Segment Assets	1,215	495
Operating Segments [Member] \| Other [Member]
Segment Profit and Loss [Abstract]
Revenues	253	(488)
Voyage Expenses	(639)	(1,612)
Amortization Expense		25
Gross Voyage Profit (Loss) (excluding Depreciation Expense)	892	1,099
Segment Assets	7,236	2,720
Expenditures for Segment Assets	$ 11,047	$ 5,211

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