Refers to the number of units.

No definition available.

Name:	ish_NumberOfUnits
Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Units Chartered To One Customer

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Vessels Employed On Long-Term Bareboat Charters

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Vessels Held For Sale

+ References

No definition available.

+ Details

Name:	ish_NumberOfVesselsHeldForSale
Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Vessels Leased

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Vessels On Time Charter To Another Company

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of vessels owned or operated by the entity as of balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Vessels Redelivered

+ References

No definition available.

+ Details

Name:	ish_NumberOfVesselsRedelivered
Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of vessels sold

+ References

No definition available.

+ Details

Name:	ish_NumberOfVesselsSold
Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the number of vessels which deploy in this segment.

+ References

No definition available.

+ Details

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Namespace Prefix:	ish_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the entity's total work force that is covered by these agreements.

+ References

No definition available.

+ Details

Name:	ish_PercentageOfTotalWorkForceCoveredByAgreement
Namespace Prefix:	ish_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Significant Operations (Narrative) (Details) $ in Thousands		2 Months Ended	3 Months Ended	12 Months Ended
Significant Operations (Narrative) (Details) $ in Thousands	Feb. 29, 2016 item	Feb. 29, 2016 item	Mar. 31, 2015 item	Dec. 31, 2015 USD ($) segment item	Dec. 31, 2014 USD ($) item	Dec. 31, 2006 item
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 259,474	$ 294,834
Number of vessels owned or operated						2
Number of operating segments \| segment				6
Percentage of total work force that is covered by collective bargaining agreements (in hundredths)				62.00%
Payment for investment in Unconsolidated Entities \| $					$ 7,887
MSP [Member]
Segment Reporting Information [Line Items]
Number of units				8	8
United States [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 162,295	$ 183,748
Asian Countries [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				53,107	62,763
Other Countries [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				369	779
Europe [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 12,702	15,143
Pure Car Truck Carriers [Member]
Segment Reporting Information [Line Items]
Number of units			7
Number of vessels sold				1
Number of vessels held for sale				1
Pure Car Truck Carriers [Member] \| MSP [Member]
Segment Reporting Information [Line Items]
Number of vessels sold				1
Pure Car Truck Carriers [Member] \| Major Japanese Shipping Company [Member]
Segment Reporting Information [Line Items]
Number of units chartered to one customer			6
Number of vessels sold				2
Container Vessels [Member] \| MSP [Member]
Segment Reporting Information [Line Items]
Number of vessels redelivered				2
Handysize Bulk Carriers [Member] \| Subsequent Event [Member]
Segment Reporting Information [Line Items]
Number of vessels sold	2
PCTC And Specialty Contracts [Member] \| MSP [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 22,900	24,500
Rail-Ferry Service [Member] \| Special Purpose vessels [Member]
Segment Reporting Information [Line Items]
Number of units				2
Total Revenues \| $				$ 31,000	$ 32,500
Number of vessels owned or operated				2	2
Jones Act [Member]
Segment Reporting Information [Line Items]
Number of vessels held for sale				1
Jones Act [Member] \| TECO And Mosaic [Member]
Segment Reporting Information [Line Items]
Number of units					6
Jones Act [Member] \| TECO [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 19,400	$ 47,000
Jones Act [Member] \| Mosaic [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 28,400	30,800
Jones Act [Member] \| Bulk Carriers [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				2
Jones Act [Member] \| Integrated Barge and Tug Unit [Member]
Segment Reporting Information [Line Items]
Number of vessels held for sale				1
Number of vessels deployed				3
Jones Act [Member] \| Integrated Barge and Tug Unit [Member] \| TECO And Mosaic [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Jones Act [Member] \| Tug [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
Jones Act [Member] \| Barge [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
Jones Act [Member] \| Harbor Tug [Member]
Segment Reporting Information [Line Items]
Number of vessels held for sale				1
Number of vessels deployed				1
Jones Act [Member] \| Belt Self-Unloading Coal Carrier [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
Jones Act [Member] \| Molten Sulphur Carrier Vessel [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
PCTC [Member] \| Major Japanese Shipping Company [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $					37,900
PCTC [Member] \| Pure Car Truck Carriers [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				5
PCTC [Member] \| Pure Car Truck Carriers [Member] \| Major Japanese Shipping Company [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 34,400
PCTC [Member] \| Pure Car Truck Carriers [Member] \| United States [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Number of vessels leased				2
Number of vessels deployed				4
PCTC [Member] \| Pure Car Truck Carriers [Member] \| International [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
PCTC [Member] \| Supplemental Cargo [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 28,000	16,100
Dry Bulk Carriers [Member] \| Mini-Bulk Carrier [Member]
Segment Reporting Information [Line Items]
Number of vessels held for sale				15
Dry Bulk Carriers [Member] \| Capesize Bulk Carrier [Member]
Segment Reporting Information [Line Items]
Number of vessels sold		2
Dry Bulk Carriers [Member] \| Handysize Bulk Carriers [Member]
Segment Reporting Information [Line Items]
Number of vessels sold				1
Dry Bulk Carriers [Member] \| Handysize Bulk Carriers [Member] \| Subsequent Event [Member]
Segment Reporting Information [Line Items]
Number of vessels sold		2
Specialty Contracts [Member] \| Subsequent Event [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated	15	15
Specialty Contracts [Member] \| MSP [Member]
Segment Reporting Information [Line Items]
Total Revenues \| $				$ 22,900	24,500
Specialty Contracts [Member] \| Container Vessels [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Number of vessels redelivered				2
Number of vessels on time charter to another company				2
Specialty Contracts [Member] \| Multi-purpose vessels [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Specialty Contracts [Member] \| Tankers [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Specialty Contracts [Member] \| Multi-Purpose Heavy Lift Vessel [Member]
Segment Reporting Information [Line Items]
Number of vessels on time charter to another company				2
Specialty Contracts [Member] \| Multi-Purpose Ice Strengthened [Member]
Segment Reporting Information [Line Items]
Number of vessels deployed				1
Saltholmen Shipping Ltd. [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				30.00%
Payment for investment in Unconsolidated Entities \| $					$ 5,800
Saltholmen Shipping Ltd. [Member] \| Chemical Tankers [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Number of vessels immediately employed on long-term bareboat charters				2
Saltholmen Shipping Ltd. [Member] \| Specialty Contracts [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				30.00%
Saltholmen Shipping Ltd. [Member] \| Specialty Contracts [Member] \| Chemical Tankers [Member]
Segment Reporting Information [Line Items]
Number of vessels immediately employed on long-term bareboat charters				2
Brattholmen Shipping Ltd. [Member] \| Asphalt Tankers [Member]
Segment Reporting Information [Line Items]
Number of vessels owned or operated				2
Percentage of ownership interest					30.00%
Payment for investment in Unconsolidated Entities \| $					$ 2,100
Number of vessels immediately employed on long-term bareboat charters					2
Brattholmen Shipping Ltd. [Member] \| Specialty Contracts [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				30.00%
Brattholmen Shipping Ltd. [Member] \| Specialty Contracts [Member] \| Asphalt Tankers [Member]
Segment Reporting Information [Line Items]
Number of vessels immediately employed on long-term bareboat charters				2
Oslo Bulk AS [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				25.00%	25.00%
Oslo Bulk AS [Member] \| Dry Bulk Carriers [Member] \| Mini-Bulk Carrier [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				25.00%
Oslo Bulk Holding Pte. Ltd. [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				23.68%
Oslo Bulk Holding Pte. Ltd. [Member] \| Dry Bulk Carriers [Member] \| Mini-Bulk Carrier [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				23.68%
Terminales Transgolfo, S.A. de C.V. [Member] \| Rail-Ferry Service [Member] \| Special Purpose vessels [Member]
Segment Reporting Information [Line Items]
Percentage of ownership interest				49.00%