Significant Operations (Reconciliation of Totals Reported for Operating Segments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Gross Voyage Profit		$ 31,646	$ 49,697
Unallocated Amounts [Abstract]
Vessel Depreciation		21,395	26,233
Other Depreciation		1,607	751
Gross Profit		8,644	22,713
Administrative and General Expenses		22,832	20,985
Impairment Loss		154,463	38,213
(Gain) Loss on Sale of Assets		(4,543)	2
Less: Net Income (Loss) of Unconsolidated Entities		(4,049)	10
Total Other Operating Expenses		168,703	59,210
Operating Loss		(160,059)	(36,497)
Interest Expense		(13,342)	(9,737)
Derivative Income (Loss)	$ (2,800)	(2,991)	132
Loss on Extinguishment of Debt		(585)	(225)
Other Income from Vessel Financing		1,833	1,858
Investment Income		30	373
Foreign Exchange Gain (Loss)		(91)	(184)
Loss before Income Taxes		(175,205)	(44,280)
Unallocated Amounts [Abstract]
Current Assets		106,778	85,494
Other Assets		2,168	4,843
Total Assets		346,302	615,287
Operating Segments [Member]
Unallocated Amounts [Abstract]
Current Assets		46,269	65,554
Total Assets		$ 297,865	$ 544,890