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Significant Operations (Segment Profit And Loss) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
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
Segment Reporting Information [Line Items]                      
Total Revenues $ 70,978us-gaap_Revenues $ 74,410us-gaap_Revenues $ 76,752us-gaap_Revenues $ 72,694us-gaap_Revenues $ 76,169us-gaap_Revenues $ 77,938us-gaap_Revenues $ 74,897us-gaap_Revenues $ 81,124us-gaap_Revenues $ 294,834us-gaap_Revenues $ 310,128us-gaap_Revenues $ 243,496us-gaap_Revenues
Intersegment Expenses Eliminated                 18,350ish_IntersegmentExpensesEliminated 17,876ish_IntersegmentExpensesEliminated 18,638ish_IntersegmentExpensesEliminated
Voyage Expenses 52,355ish_VoyageExpenses [1] 55,450ish_VoyageExpenses [1] 57,802ish_VoyageExpenses [1] 57,433ish_VoyageExpenses [1] 52,269ish_VoyageExpenses [1] 60,395ish_VoyageExpenses [1] 58,067ish_VoyageExpenses [1] 65,970ish_VoyageExpenses [1] 223,040ish_VoyageExpenses 236,701ish_VoyageExpenses 178,860ish_VoyageExpenses
Amortization Expenses                 22,107ish_AmortizationOfIntangibleAssetsAndDryDock 16,386ish_AmortizationOfIntangibleAssetsAndDryDock 9,601ish_AmortizationOfIntangibleAssetsAndDryDock
Loss (Income) of Unconsolidated Entities                 (10)us-gaap_IncomeLossFromEquityMethodInvestments 1,661us-gaap_IncomeLossFromEquityMethodInvestments 215us-gaap_IncomeLossFromEquityMethodInvestments
Gross Voyage Profit (Loss)                 49,697us-gaap_GrossProfit 55,380us-gaap_GrossProfit 54,820us-gaap_GrossProfit
Gross Voyage Profit Margin Percentage (in hundredths)                 17.00%ish_GrossVoyageProfitMarginPercentage 18.00%ish_GrossVoyageProfitMarginPercentage 23.00%ish_GrossVoyageProfitMarginPercentage
Segment Assets 477,133ish_SegmentAssets       507,957ish_SegmentAssets       477,133ish_SegmentAssets 507,957ish_SegmentAssets 492,798ish_SegmentAssets
Expenditures for Segment Assets 79,701ish_ExpendituresForSegmentAssets       72,480ish_ExpendituresForSegmentAssets       79,701ish_ExpendituresForSegmentAssets 72,480ish_ExpendituresForSegmentAssets 146,188ish_ExpendituresForSegmentAssets
Intersegment Eliminations [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 (18,350)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember		 (17,876)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember		 (18,638)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember
External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 294,834us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember		 310,128us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember		 243,496us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
Jones Act [Member]                      
Segment Reporting Information [Line Items]                      
Voyage Expenses                 82,913ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 84,942ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 24,430ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Amortization Expenses                 15,813ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 10,285ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 2,800ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Gross Voyage Profit (Loss)                 26,128us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 27,524us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 6,491us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Gross Voyage Profit Margin Percentage (in hundredths)                 21.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 22.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 19.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Segment Assets 126,936ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]       150,529ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]       126,936ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 150,529ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 119,377ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Expenditures for Segment Assets 9,528ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]       41,973ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]       9,528ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 41,973ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 90,319ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
Jones Act [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 124,854us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 122,751us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2] 33,721us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_JonesActMember		 [2]
PCTC [Member]                      
Segment Reporting Information [Line Items]                      
Voyage Expenses                 65,696ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 77,078ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 83,233ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Amortization Expenses                 2,606ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 2,077ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 2,455ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Gross Voyage Profit (Loss)                 9,779us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 15,453us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 27,833us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Gross Voyage Profit Margin Percentage (in hundredths)                 13.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 16.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 25.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Segment Assets 159,203ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		       117,252ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		       159,203ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 117,252ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 122,403ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Expenditures for Segment Assets 62,155ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		       23,324ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		       62,155ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 23,324ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 5,969ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
PCTC [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 78,081us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 94,608us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember		 113,521us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_TrucksMember
Dry Bulk Carriers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 18,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 21,100us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 26,100us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Voyage Expenses                 13,327ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 17,588ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 16,559ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Amortization Expenses                 236ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 837ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 2,576ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Loss (Income) of Unconsolidated Entities                 468us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 1,587us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 (75)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Gross Voyage Profit (Loss)                 4,014us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 1,086us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 7,020us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Gross Voyage Profit Margin Percentage (in hundredths)                 22.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 5.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 27.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Segment Assets 122,401ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		       158,521ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		       122,401ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 158,521ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 162,921ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Expenditures for Segment Assets 1,949ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		       3,043ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		       1,949ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 3,043ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 21,899ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Dry Bulk Carriers [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 18,045us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 21,098us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember		 26,080us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_DryBulkCarriersMember
Rail-Ferry Service [Member]                      
Segment Reporting Information [Line Items]                      
Voyage Expenses                 28,743ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 29,166ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 28,435ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Amortization Expenses                 994ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 1,054ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 1,040ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Loss (Income) of Unconsolidated Entities                 193us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 74us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 290us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Gross Voyage Profit (Loss)                 4,647us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 6,889us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 3,570us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Gross Voyage Profit Margin Percentage (in hundredths)                 13.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 19.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 11.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Segment Assets 43,776ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		       32,982ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		       43,776ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 32,982ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 35,196ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Expenditures for Segment Assets 363ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		       763ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		       363ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 763ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 3,766ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Rail-Ferry Service [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 34,577us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 37,183us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember		 33,335us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_RailFerryServiceMember
Specialty Contracts [Member]                      
Segment Reporting Information [Line Items]                      
Voyage Expenses                 33,973ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 29,057ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 26,141ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Amortization Expenses                 2,433ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 2,133ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 730ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Loss (Income) of Unconsolidated Entities                 (671)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		    
Gross Voyage Profit (Loss)                 4,030us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 3,293us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 8,655us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Gross Voyage Profit Margin Percentage (in hundredths)                 10.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 10.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 24.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Segment Assets 18,644ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		       25,467ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		       18,644ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 25,467ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 27,767ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Expenditures for Segment Assets 495ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		       3,116ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		       495ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 3,116ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 23,695ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Specialty Contracts [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 39,765us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 34,483us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember		 35,526us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= ish_SpecialtyContractsMember
Other [Member]                      
Segment Reporting Information [Line Items]                      
Intersegment Expenses Eliminated                 18,350ish_IntersegmentExpensesEliminated
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 17,876ish_IntersegmentExpensesEliminated
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 18,638ish_IntersegmentExpensesEliminated
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Voyage Expenses                 (1,612)ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 (1,130)ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 62ish_VoyageExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Amortization Expenses                 25ish_AmortizationOfIntangibleAssetsAndDryDock
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		    
Gross Voyage Profit (Loss)                 1,099us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 1,135us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 1,251us-gaap_GrossProfit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Gross Voyage Profit Margin Percentage (in hundredths)                 (225.00%)ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 227.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 95.00%ish_GrossVoyageProfitMarginPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Segment Assets 6,173ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		       23,206ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		       6,173ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 23,206ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 25,134ish_SegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Expenditures for Segment Assets 5,211ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		       261ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		       5,211ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 261ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 540ish_ExpendituresForSegmentAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Other [Member] | Intersegment Eliminations [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 (18,350)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 (17,876)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 (18,638)us-gaap_Revenues
/ us-gaap_ConsolidationItemsAxis
= us-gaap_IntersegmentEliminationMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
Other [Member] | External Customers [Member]                      
Segment Reporting Information [Line Items]                      
Total Revenues                 $ (488)us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 $ 5us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember		 $ 1,313us-gaap_Revenues
/ us-gaap_MajorCustomersAxis
= ish_ExternalCustomersMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember
[1] Certain previously reported amounts have been reclassified out of voyage expense and into amortization and depreciation expense to conform to the 2014 presentation.
[2] 2012 reflects one month of UOS.