Significant Operations (Reconciliation Of The Totals Reported For The Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of profit (loss) from segments to consolidated [Abstract]
Total Gross Voyage Profit for Reportable Segments										$ 49,697	$ 55,380	$ 54,820
Unallocated Amounts [Abstract]
Vessel and Other Depreciation										(26,984)	(24,930)	(24,975)
Administrative and General Expenses										(20,985)	(22,378)	(22,714)
Impairment Loss										(38,213)
(Loss)/Gain on Sale of Other Assets	3,800									(2)	(16)	16,625
Loss (Income) of Unconsolidated Entities										(10)	1,661	215
Operating (Loss) Income		(36,975)	1,074	1,660	(2,256)	6,048	1,959	1,404	306	(36,497)	9,717	23,971
Interest Expense										(9,962)	(9,504)	(10,409)
Derivative Income (Loss)										132	(438)	(485)
Gain on Sale of Investment												580
Investment Income										373	114	470
Other Income from Vessel Financing										1,858	2,122	2,387
Foreign Exchange Gain (Loss)										(184)	5,914	5,506
(Loss) Income before Income Taxes										(44,280)	7,925	22,020
Reconciliation of assets from segments to consolidated [Abstract]
Total Assets for Reportable Segments		477,133				507,957				477,133	507,957	492,798
Unallocated Amounts [Abstract]
Current Assets		85,494				86,841				85,494	86,841
Investment in Unconsolidated Entities		21,837				14,818				21,837	14,818
Due from Related Parties		1,660				1,974				1,660	1,974
Other Assets		4,843				7,383				4,843	7,383
Goodwill		2,735				2,735				2,735	2,735
Deferred Tax Assets						7,325					7,325
Notes Receivable		24,455				27,659				24,455	27,659
TOTAL ASSETS		$ 618,157				$ 656,692				$ 618,157	$ 656,692