Segment Information (Operating Results, Capital Expenditures And Assets By Reportable Segments) (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Operating Revenues	$ 197,038,000		$ 281,609,000	$ 410,966,000	$ 542,253,000
Costs and Expenses [Abstract]
Administrative and general	34,175,000		38,674,000	69,879,000	77,561,000
Depreciation and amortization	31,361,000		32,079,000	62,350,000	63,509,000
Total costs and expenses	209,418,000		278,496,000	433,579,000	547,961,000
Gains (Losses) on Asset Dispositions and Impairments, Net	(17,771,000)		4,386,000	(17,554,000)	(460,000)
Operating Income (Loss)	(30,151,000)		7,499,000	(40,167,000)	(6,168,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	(1,555,000)		1,426,000	1,065,000	(1,570,000)
Foreign currency gains (losses), net	(22,000)		2,436,000	15,000	443,000
Other, net	(7,652,000)		4,433,000	(7,384,000)	4,389,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(7,162,000)		1,064,000	(7,211,000)	4,963,000
Loss Before Taxes and Equity Earnings	(69,530,000)		(9,410,000)	(104,836,000)	(43,164,000)
Capital Expenditures		$ 204,100,000		204,074,000	132,128,000
Property, Plant and Equipment, Gross	2,158,826,000			2,158,826,000		$ 2,123,201,000
Accumulated depreciation	(997,214,000)			(997,214,000)		(994,181,000)
Construction in progress	402,090,000			402,090,000		454,605,000
Net property and equipment	1,563,702,000			1,563,702,000		1,583,625,000
Inventories	16,798,000			16,798,000		24,768,000
Goodwill	52,394,000			52,394,000		52,340,000
Intangible Assets, Net	24,116,000			24,116,000		26,392,000
Total assets	3,001,317,000		3,164,867,000	3,001,317,000	3,164,867,000	$ 3,185,419,000
Offshore Marine Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	57,244,000		96,689,000	117,097,000	190,110,000
Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	33,399,000		60,543,000	72,427,000	116,379,000
Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	55,620,000		55,674,000	112,675,000	107,081,000
Illinois Corn Processing LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	40,576,000		48,371,000	90,185,000	87,969,000
Other Income and Expenses [Abstract]
Sales Revenue, Goods, Net				84,900,000	82,300,000
Cost of Goods Sold				77,200,000	68,000,000
Inventory, Raw Materials	1,000,000		1,700,000	1,000,000	1,700,000
Inventory, Work in Process	1,300,000		1,600,000	1,300,000	1,600,000
Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	10,199,000		20,332,000	18,582,000	40,714,000
Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0		0	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	197,038,000		281,609,000	410,966,000	542,253,000
Costs and Expenses [Abstract]
Operating Expenses	143,882,000		207,743,000	301,350,000	406,891,000
Administrative and general	34,175,000		38,674,000	69,879,000	77,561,000
Depreciation and amortization	31,361,000		32,079,000	62,350,000	63,509,000
Total costs and expenses	209,418,000		278,496,000	433,579,000	547,961,000
Gains (Losses) on Asset Dispositions and Impairments, Net	(17,771,000)		4,386,000	(17,554,000)	(460,000)
Operating Income (Loss)	(30,151,000)		7,499,000	(40,167,000)	(6,168,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	(1,555,000)		1,426,000	1,065,000	(1,570,000)
Foreign currency gains (losses), net	(22,000)		2,436,000	15,000	443,000
Other, net	(7,652,000)		4,433,000	(7,384,000)	4,389,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(7,162,000)		1,064,000	(7,211,000)	4,963,000
Capital Expenditures				204,074,000	132,128,000
Property, Plant and Equipment, Gross	2,158,826,000		2,100,309,000	2,158,826,000	2,100,309,000
Accumulated depreciation	(997,214,000)		(954,931,000)	(997,214,000)	(954,931,000)
Property, Plant and Equipment, Net In Service	1,161,612,000		1,145,378,000	1,161,612,000	1,145,378,000
Construction in progress	402,090,000		399,033,000	402,090,000	399,033,000
Net property and equipment	1,563,702,000		1,544,411,000	1,563,702,000	1,544,411,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	325,386,000		482,302,000	325,386,000	482,302,000
Inventories	16,798,000		19,736,000	16,798,000	19,736,000
Goodwill	52,394,000		62,686,000	52,394,000	62,686,000
Intangible Assets, Net	24,116,000		30,742,000	24,116,000	30,742,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	209,750,000		286,621,000	209,750,000	286,621,000
Operating Segments [Member] | Offshore Marine Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	57,271,000		96,715,000	117,150,000	190,171,000
Costs and Expenses [Abstract]
Operating Expenses	44,245,000		72,173,000	93,095,000	146,528,000
Administrative and general	11,929,000		12,655,000	24,327,000	26,214,000
Depreciation and amortization	15,254,000		15,692,000	30,092,000	31,058,000
Total costs and expenses	71,428,000		100,520,000	147,514,000	203,800,000
Gains (Losses) on Asset Dispositions and Impairments, Net	(20,357,000)		3,455,000	(20,737,000)	(3,194,000)
Operating Income (Loss)	(34,514,000)		(350,000)	(51,101,000)	(16,823,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	163,000		4,000	3,061,000	(5,000)
Foreign currency gains (losses), net	(819,000)		1,907,000	(2,379,000)	1,890,000
Other, net	0		43,000	265,000	(103,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(3,315,000)		2,826,000	(1,154,000)	5,801,000
Segment Profit (Loss)	(38,485,000)		4,430,000	(51,308,000)	(9,240,000)
Capital Expenditures				45,840,000	53,118,000
Property, Plant and Equipment, Gross	1,098,914,000		1,072,937,000	1,098,914,000	1,072,937,000
Accumulated depreciation	(556,909,000)		(525,937,000)	(556,909,000)	(525,937,000)
Property, Plant and Equipment, Net In Service	542,005,000		547,000,000	542,005,000	547,000,000
Construction in progress	101,914,000		103,992,000	101,914,000	103,992,000
Net property and equipment	643,919,000		650,992,000	643,919,000	650,992,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	130,034,000		126,601,000	130,034,000	126,601,000
Inventories	3,219,000		5,583,000	3,219,000	5,583,000
Goodwill	0		13,367,000	0	13,367,000
Intangible Assets, Net	0		1,113,000	0	1,113,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	98,456,000		103,444,000	98,456,000	103,444,000
Total assets	875,628,000		901,100,000	875,628,000	901,100,000
Operating Segments [Member] | Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	33,814,000		61,150,000	73,428,000	117,757,000
Costs and Expenses [Abstract]
Operating Expenses	27,446,000		48,556,000	57,564,000	90,069,000
Administrative and general	3,777,000		3,765,000	7,689,000	7,649,000
Depreciation and amortization	6,254,000		7,362,000	13,391,000	14,251,000
Total costs and expenses	37,477,000		59,683,000	78,644,000	111,969,000
Gains (Losses) on Asset Dispositions and Impairments, Net	2,580,000		1,166,000	3,185,000	2,969,000
Operating Income (Loss)	(1,083,000)		2,633,000	(2,031,000)	8,757,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0		177,000	0	259,000
Foreign currency gains (losses), net	1,018,000		208,000	2,455,000	(913,000)
Other, net	(4,000)		0	(4,000)	0
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(1,677,000)		(3,717,000)	(4,455,000)	(3,991,000)
Segment Profit (Loss)	(1,746,000)		(699,000)	(4,035,000)	4,112,000
Capital Expenditures				7,705,000	12,702,000
Property, Plant and Equipment, Gross	386,216,000		492,508,000	386,216,000	492,508,000
Accumulated depreciation	(154,893,000)		(169,677,000)	(154,893,000)	(169,677,000)
Property, Plant and Equipment, Net In Service	231,323,000		322,831,000	231,323,000	322,831,000
Construction in progress	7,663,000		27,352,000	7,663,000	27,352,000
Net property and equipment	238,986,000		350,183,000	238,986,000	350,183,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	79,154,000		100,700,000	79,154,000	100,700,000
Inventories	1,824,000		2,085,000	1,824,000	2,085,000
Goodwill	2,418,000		2,500,000	2,418,000	2,500,000
Intangible Assets, Net	5,521,000		6,461,000	5,521,000	6,461,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	45,428,000		70,975,000	45,428,000	70,975,000
Total assets	373,331,000		532,904,000	373,331,000	532,904,000
Operating Segments [Member] | Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	55,620,000		55,674,000	112,675,000	107,081,000
Costs and Expenses [Abstract]
Operating Expenses	30,269,000		36,124,000	57,503,000	73,255,000
Administrative and general	7,337,000		6,676,000	14,255,000	12,965,000
Depreciation and amortization	7,415,000		6,611,000	13,977,000	13,346,000
Total costs and expenses	45,021,000		49,411,000	85,735,000	99,566,000
Gains (Losses) on Asset Dispositions and Impairments, Net	6,000		0	0	0
Operating Income (Loss)	10,605,000		6,263,000	26,940,000	7,515,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0		0	0	0
Foreign currency gains (losses), net	(6,000)		9,000	(9,000)	(3,000)
Other, net	(928,000)		187,000	(927,000)	216,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(1,591,000)		2,363,000	(1,565,000)	3,504,000
Segment Profit (Loss)	8,080,000		8,822,000	24,439,000	11,232,000
Capital Expenditures				148,410,000	63,421,000
Property, Plant and Equipment, Gross	588,649,000		454,076,000	588,649,000	454,076,000
Accumulated depreciation	(244,910,000)		(226,127,000)	(244,910,000)	(226,127,000)
Property, Plant and Equipment, Net In Service	343,739,000		227,949,000	343,739,000	227,949,000
Construction in progress	290,582,000		264,191,000	290,582,000	264,191,000
Net property and equipment	634,321,000		492,140,000	634,321,000	492,140,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	56,385,000		206,889,000	56,385,000	206,889,000
Inventories	799,000		878,000	799,000	878,000
Goodwill	1,852,000		1,852,000	1,852,000	1,852,000
Intangible Assets, Net	0		0	0	0
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	27,477,000		29,241,000	27,477,000	29,241,000
Total assets	720,834,000		731,000,000	720,834,000	731,000,000
Operating Segments [Member] | Illinois Corn Processing LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	40,576,000		48,371,000	90,185,000	87,969,000
Costs and Expenses [Abstract]
Operating Expenses	36,153,000		40,588,000	82,442,000	73,706,000
Administrative and general	912,000		509,000	1,568,000	1,071,000
Depreciation and amortization	1,064,000		979,000	2,117,000	1,959,000
Total costs and expenses	38,129,000		42,076,000	86,127,000	76,736,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0		0	0	0
Operating Income (Loss)	2,447,000		6,295,000	4,058,000	11,233,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	856,000		50,000	669,000	(778,000)
Foreign currency gains (losses), net	0		0	0	0
Other, net	0		4,112,000	0	4,112,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	0		0	0	0
Segment Profit (Loss)	3,303,000		10,457,000	4,727,000	14,567,000
Capital Expenditures				2,244,000	2,519,000
Property, Plant and Equipment, Gross	51,475,000		47,256,000	51,475,000	47,256,000
Accumulated depreciation	(21,507,000)		(17,447,000)	(21,507,000)	(17,447,000)
Property, Plant and Equipment, Net In Service	29,968,000		29,809,000	29,968,000	29,809,000
Construction in progress	3,455,000		3,237,000	3,455,000	3,237,000
Net property and equipment	33,423,000		33,046,000	33,423,000	33,046,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	0		0	0	0
Inventories	10,857,000		11,190,000	10,857,000	11,190,000
Goodwill	0		0	0	0
Intangible Assets, Net	0		0	0	0
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	11,642,000		10,086,000	11,642,000	10,086,000
Total assets	55,922,000		54,322,000	55,922,000	54,322,000
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	10,261,000		20,337,000	18,680,000	40,789,000
Costs and Expenses [Abstract]
Operating Expenses	6,427,000		11,103,000	12,232,000	24,933,000
Administrative and general	3,649,000		6,617,000	7,872,000	13,753,000
Depreciation and amortization	448,000		489,000	903,000	989,000
Total costs and expenses	10,524,000		18,209,000	21,007,000	39,675,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0		(235,000)	(2,000)	(235,000)
Operating Income (Loss)	(263,000)		1,893,000	(2,329,000)	879,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0		304,000	0	(472,000)
Foreign currency gains (losses), net	(73,000)		36,000	(100,000)	(4,000)
Other, net	(6,723,000)		40,000	(6,723,000)	48,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(579,000)		(408,000)	(37,000)	(351,000)
Segment Profit (Loss)	(7,638,000)		1,865,000	(9,189,000)	100,000
Capital Expenditures				0	26,000
Property, Plant and Equipment, Gross	2,861,000		3,146,000	2,861,000	3,146,000
Accumulated depreciation	(2,476,000)		(2,901,000)	(2,476,000)	(2,901,000)
Property, Plant and Equipment, Net In Service	385,000		245,000	385,000	245,000
Construction in progress	0		0	0	0
Net property and equipment	385,000		245,000	385,000	245,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	59,813,000		48,112,000	59,813,000	48,112,000
Inventories	99,000		0	99,000	0
Goodwill	48,124,000		44,967,000	48,124,000	44,967,000
Intangible Assets, Net	18,595,000		23,168,000	18,595,000	23,168,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	22,944,000		61,592,000	22,944,000	61,592,000
Total assets	149,960,000		178,084,000	149,960,000	178,084,000
Operating Segments [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(504,000)		(638,000)	(1,152,000)	(1,514,000)
Costs and Expenses [Abstract]
Operating Expenses	(658,000)		(801,000)	(1,486,000)	(1,600,000)
Administrative and general	6,571,000		8,452,000	14,168,000	15,909,000
Depreciation and amortization	926,000		946,000	1,870,000	1,906,000
Total costs and expenses	6,839,000		8,597,000	14,552,000	16,215,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0		0	0	0
Operating Income (Loss)	(7,343,000)		(9,235,000)	(15,704,000)	(17,729,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	(2,574,000)		891,000	(2,665,000)	(574,000)
Foreign currency gains (losses), net	(142,000)		276,000	48,000	(527,000)
Other, net	3,000		51,000	5,000	116,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	0		0	0	0
Capital Expenditures				(125,000)	342,000
Property, Plant and Equipment, Gross	30,711,000		30,386,000	30,711,000	30,386,000
Accumulated depreciation	(16,519,000)		(12,842,000)	(16,519,000)	(12,842,000)
Property, Plant and Equipment, Net In Service	14,192,000		17,544,000	14,192,000	17,544,000
Construction in progress	(1,524,000)		261,000	(1,524,000)	261,000
Net property and equipment	12,668,000		17,805,000	12,668,000	17,805,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	0		0	0	0
Inventories	0		0	0	0
Goodwill	0		0	0	0
Intangible Assets, Net	0		0	0	0
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	3,803,000		11,283,000	3,803,000	11,283,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0		0	0	0
Intersegment Eliminations [Member] | Offshore Marine Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(27,000)		26,000	(53,000)	61,000
Intersegment Eliminations [Member] | Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(415,000)		607,000	(1,001,000)	1,378,000
Intersegment Eliminations [Member] | Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0		0	0	0
Intersegment Eliminations [Member] | Illinois Corn Processing LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0		0	0	0
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(62,000)		5,000	(98,000)	75,000
Intersegment Eliminations [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	504,000		(638,000)	1,152,000	(1,514,000)
Segment Reconciling Items [Member]
Other Income and Expenses [Abstract]
Other Income (Expense) not included in Segment Profit (Loss)	30,150,000		25,204,000	58,365,000	40,258,000
Less Equity Earnings included in Segment Profit (Loss)	7,162,000		(1,064,000)	7,211,000	(4,963,000)
Cash And Near Cash Assets	$ 809,171,000		$ 738,369,000	$ 809,171,000	$ 738,369,000