Segment Information (Operating Results, Capital Expenditures And Assets By Reportable Segments) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating Revenues	$ 115,791,000	$ 99,647,000	$ 234,205,000	$ 204,699,000
Costs and Expenses [Abstract]
Administrative and general	25,540,000	21,361,000	48,418,000	44,037,000
Depreciation and amortization	17,469,000	15,043,000	34,188,000	30,141,000
Total costs and expenses	112,695,000	100,431,000	227,504,000	201,241,000
Gains (Losses) on Asset Dispositions and Impairments, Net	5,897,000	2,586,000	5,709,000	3,183,000
Operating Income (Loss)	8,993,000	1,802,000	12,410,000	6,641,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	16,897,000	(2,574,000)	19,727,000	(2,665,000)
Foreign currency gains (losses), net	(1,470,000)	797,000	(71,000)	2,394,000
Other, net	424,000	(7,652,000)	4,000	(7,649,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	2,333,000	(3,847,000)	2,441,000	(6,057,000)
Loss Before Taxes and Equity Earnings	(6,453,000)	(33,550,000)	13,439,000	(50,740,000)
Capital Expenditures			80,987,000	155,990,000
Property, Plant and Equipment, Gross	1,340,400,000		1,340,400,000		$ 1,178,556,000
Accumulated depreciation	467,925,000		467,925,000		444,559,000
Construction in progress	133,537,000		133,537,000		246,010,000
Net property and equipment	1,006,012,000		1,006,012,000		980,007,000
Inventories	2,444,000		2,444,000		2,582,000
Goodwill	32,749,000		32,749,000		32,758,000
Intangible Assets, Net	18,931,000		18,931,000		20,078,000
Disposal Group, Including Discontinued Operation, Assets	55,700,000	1,200,824,000	55,700,000	1,200,824,000
Total assets	1,773,885,000	3,001,317,000	1,773,885,000	3,001,317,000	$ 2,862,321,000
Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	37,644,000	33,814,000	80,313,000	73,428,000
Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	72,023,000	55,620,000	139,662,000	112,675,000
Witt O'Brien's LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	6,008,000	10,098,000	13,998,000	18,346,000
Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	116,000	115,000	232,000	250,000
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	115,791,000	99,647,000	234,205,000	204,699,000
Costs and Expenses [Abstract]
Operating Expenses	69,686,000	64,027,000	144,898,000	127,063,000
Administrative and general	25,540,000	21,361,000	48,418,000	44,037,000
Depreciation and amortization	17,469,000	15,043,000	34,188,000	30,141,000
Total costs and expenses	112,695,000	100,431,000	227,504,000	201,241,000
Gains (Losses) on Asset Dispositions and Impairments, Net	5,897,000	2,586,000	5,709,000	3,183,000
Operating Income (Loss)	8,993,000	1,802,000	12,410,000	6,641,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	16,897,000	(2,574,000)	19,727,000	(2,665,000)
Foreign currency gains (losses), net	(1,470,000)	797,000	(71,000)	2,394,000
Other, net	424,000	(7,652,000)	4,000	(7,649,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	2,333,000	(3,847,000)	2,441,000	(6,057,000)
Capital Expenditures			80,987,000	155,990,000
Property, Plant and Equipment, Gross	1,340,400,000	1,008,437,000	1,340,400,000	1,008,437,000
Accumulated depreciation	467,925,000	418,798,000	467,925,000	418,798,000
Property, Plant and Equipment, Net In Service	872,475,000	589,639,000	872,475,000	589,639,000
Construction in progress	133,537,000	296,721,000	133,537,000	296,721,000
Net property and equipment	1,006,012,000	886,360,000	1,006,012,000	886,360,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	174,106,000	195,352,000	174,106,000	195,352,000
Inventories	2,444,000	2,722,000	2,444,000	2,722,000
Goodwill	32,749,000	52,394,000	32,749,000	52,394,000
Intangible Assets, Net	18,931,000	24,116,000	18,931,000	24,116,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	118,029,000	99,652,000	118,029,000	99,652,000
Operating Segments [Member] | Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	37,644,000	33,814,000	80,313,000	73,428,000
Costs and Expenses [Abstract]
Operating Expenses	31,902,000	27,446,000	64,471,000	57,564,000
Administrative and general	4,725,000	3,777,000	8,517,000	7,689,000
Depreciation and amortization	6,483,000	6,254,000	13,075,000	13,391,000
Total costs and expenses	43,110,000	37,477,000	86,063,000	78,644,000
Gains (Losses) on Asset Dispositions and Impairments, Net	5,891,000	2,580,000	6,124,000	3,185,000
Operating Income (Loss)	425,000	(1,083,000)	374,000	(2,031,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0	0	0	0
Foreign currency gains (losses), net	(1,630,000)	1,018,000	(262,000)	2,455,000
Other, net	0	(4,000)	0	(4,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(1,264,000)	(1,677,000)	(3,642,000)	(4,455,000)
Segment Profit (Loss)	(2,469,000)	(1,746,000)	(3,530,000)	(4,035,000)
Capital Expenditures			22,754,000	7,705,000
Property, Plant and Equipment, Gross	421,117,000	386,216,000	421,117,000	386,216,000
Accumulated depreciation	170,162,000	154,893,000	170,162,000	154,893,000
Property, Plant and Equipment, Net In Service	250,955,000	231,323,000	250,955,000	231,323,000
Construction in progress	17,598,000	7,663,000	17,598,000	7,663,000
Net property and equipment	268,553,000	238,986,000	268,553,000	238,986,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	66,956,000	79,154,000	66,956,000	79,154,000
Inventories	1,517,000	1,824,000	1,517,000	1,824,000
Goodwill	2,391,000	2,418,000	2,391,000	2,418,000
Intangible Assets, Net	11,238,000	5,521,000	11,238,000	5,521,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	42,253,000	45,428,000	42,253,000	45,428,000
Total assets	392,908,000	373,331,000	392,908,000	373,331,000
Operating Segments [Member] | Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	72,023,000	55,620,000	139,662,000	112,675,000
Costs and Expenses [Abstract]
Operating Expenses	33,850,000	30,269,000	71,204,000	57,503,000
Administrative and general	8,028,000	7,337,000	15,116,000	14,255,000
Depreciation and amortization	10,115,000	7,415,000	19,276,000	13,977,000
Total costs and expenses	51,993,000	45,021,000	105,596,000	85,735,000
Gains (Losses) on Asset Dispositions and Impairments, Net	6,000	6,000	(415,000)	0
Operating Income (Loss)	20,036,000	10,605,000	33,651,000	26,940,000
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0	0	0	0
Foreign currency gains (losses), net	8,000	(6,000)	3,000	(9,000)
Other, net	421,000	(928,000)	59,000	(927,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	5,621,000	(1,591,000)	6,657,000	(1,565,000)
Segment Profit (Loss)	26,086,000	8,080,000	40,370,000	24,439,000
Capital Expenditures			58,018,000	148,410,000
Property, Plant and Equipment, Gross	888,563,000	588,649,000	888,563,000	588,649,000
Accumulated depreciation	277,257,000	244,910,000	277,257,000	244,910,000
Property, Plant and Equipment, Net In Service	611,306,000	343,739,000	611,306,000	343,739,000
Construction in progress	115,939,000	290,582,000	115,939,000	290,582,000
Net property and equipment	727,245,000	634,321,000	727,245,000	634,321,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	48,486,000	56,385,000	48,486,000	56,385,000
Inventories	744,000	799,000	744,000	799,000
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	24,367,000	27,477,000	24,367,000	27,477,000
Total assets	802,694,000	720,834,000	802,694,000	720,834,000
Operating Segments [Member] | Witt O'Brien's LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	6,061,000	10,146,000	14,069,000	18,430,000
Costs and Expenses [Abstract]
Operating Expenses	4,043,000	6,427,000	9,415,000	12,232,000
Administrative and general	2,462,000	3,475,000	5,681,000	7,448,000
Depreciation and amortization	205,000	448,000	407,000	903,000
Total costs and expenses	6,710,000	10,350,000	15,503,000	20,583,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0	0	0	(2,000)
Operating Income (Loss)	(649,000)	(204,000)	(1,434,000)	(2,155,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0	0	0	0
Foreign currency gains (losses), net	23,000	(74,000)	33,000	(100,000)
Other, net	0	0	0	0
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(20,000)	100,000	137,000	186,000
Segment Profit (Loss)	(646,000)	(178,000)	(1,264,000)	(2,069,000)
Capital Expenditures			60,000	0
Property, Plant and Equipment, Gross	1,227,000	2,861,000	1,227,000	2,861,000
Accumulated depreciation	892,000	2,476,000	892,000	2,476,000
Property, Plant and Equipment, Net In Service	335,000	385,000	335,000	385,000
Construction in progress	0	0	0	0
Net property and equipment	335,000	385,000	335,000	385,000
Investments, at Equity, and Advances to 50% or Less Owned Companies	663,000	611,000	663,000	611,000
Inventories	183,000	99,000	183,000	99,000
Goodwill	28,506,000	48,124,000	28,506,000	48,124,000
Intangible Assets, Net	7,693,000	18,595,000	7,693,000	18,595,000
Other Current And Long-Term Assets, Excluding Cash And Near Cash Assets	13,190,000	14,983,000	13,190,000	14,983,000
Total assets	50,570,000	82,797,000	50,570,000	82,797,000
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	116,000	115,000	232,000	250,000
Costs and Expenses [Abstract]
Operating Expenses	0	0	0	0
Administrative and general	225,000	174,000	379,000	424,000
Depreciation and amortization	0	0	0	0
Total costs and expenses	225,000	174,000	379,000	424,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0	0	0	0
Operating Income (Loss)	(109,000)	(59,000)	(147,000)	(174,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	0	0	0	0
Foreign currency gains (losses), net	0	1,000	0	0
Other, net	0	(6,723,000)	(300,000)	(6,723,000)
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	(2,004,000)	(679,000)	(711,000)	(223,000)
Segment Profit (Loss)	(2,113,000)	(7,460,000)	(1,158,000)	(7,120,000)
Capital Expenditures			0	0
Property, Plant and Equipment, Gross	0	0	0	0
Accumulated depreciation	0	0	0	0
Property, Plant and Equipment, Net In Service	0	0	0	0
Construction in progress	0	0	0	0
Net property and equipment	0	0	0	0
Investments, at Equity, and Advances to 50% or Less Owned Companies	58,001,000	59,202,000	58,001,000	59,202,000
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	11,427,000	7,961,000	11,427,000	7,961,000
Total assets	69,428,000	67,163,000	69,428,000	67,163,000
Operating Segments [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(53,000)	(48,000)	(71,000)	(84,000)
Costs and Expenses [Abstract]
Operating Expenses	(109,000)	(115,000)	(192,000)	(236,000)
Administrative and general	10,100,000	6,598,000	18,725,000	14,221,000
Depreciation and amortization	666,000	926,000	1,430,000	1,870,000
Total costs and expenses	10,657,000	7,409,000	19,963,000	15,855,000
Gains (Losses) on Asset Dispositions and Impairments, Net	0	0	0	0
Operating Income (Loss)	(10,710,000)	(7,457,000)	(20,034,000)	(15,939,000)
Other Income and Expenses [Abstract]
Derivative gains (losses), net	16,897,000	(2,574,000)	19,727,000	(2,665,000)
Foreign currency gains (losses), net	129,000	(142,000)	155,000	48,000
Other, net	3,000	3,000	245,000	5,000
Equity in Earnings (Losses) of 50% or Less Owned Companies, Net of Tax	0	0	0	0
Capital Expenditures			155,000	(125,000)
Property, Plant and Equipment, Gross	29,493,000	30,711,000	29,493,000	30,711,000
Accumulated depreciation	19,614,000	16,519,000	19,614,000	16,519,000
Property, Plant and Equipment, Net In Service	9,879,000	14,192,000	9,879,000	14,192,000
Construction in progress	0	(1,524,000)	0	(1,524,000)
Net property and equipment	9,879,000	12,668,000	9,879,000	12,668,000
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	26,792,000	3,803,000	26,792,000	3,803,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations [Member] | Inland River Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations [Member] | Shipping Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations [Member] | Witt O'Brien's LLC [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(53,000)	(48,000)	(71,000)	84,000
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Eliminations [Member] | Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	53,000	48,000	71,000	(84,000)
Segment Reconciling Items [Member]
Other Income and Expenses [Abstract]
Other Income (Expense) not included in Segment Profit (Loss)	31,297,000	25,923,000	18,631,000	49,461,000
Less Equity Earnings included in Segment Profit (Loss)	(2,333,000)	3,847,000	(2,441,000)	6,057,000
Cash And Near Cash Assets	$ 365,914,000	$ 539,897,000	$ 365,914,000	$ 539,897,000