v2.4.1.9

PROPERTY, PLANT, EQUIPMENT, AND MINERAL PROPERTIES (Schedule of Property, Plant, Equipment, and Mineral Properties) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	$ 907,002us-gaap_PropertyPlantAndEquipmentGross	$ 904,382us-gaap_PropertyPlantAndEquipmentGross
Accumulated depreciation	(288,768)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	(271,294)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Depreciable assets, net	618,234ipi_Depreciableassetsnet	633,088ipi_Depreciableassetsnet
Mineral properties and development costs	163,741us-gaap_MineralPropertiesGross	163,197us-gaap_MineralPropertiesGross
Accumulated depletion	(19,508)us-gaap_MineralPropertiesAccumulatedDepletion	(17,544)us-gaap_MineralPropertiesAccumulatedDepletion
Total depletable assets, net	144,233ipi_MineralPropertiesAndDevelopmentCostsNet	145,653ipi_MineralPropertiesAndDevelopmentCostsNet
Property, Plant, Equipment and Mineral Properties, Net	770,188us-gaap_PropertyPlantAndEquipmentNet	785,250us-gaap_PropertyPlantAndEquipmentNet
Building and Building Improvements [Member]
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	269,090us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingAndBuildingImprovementsMember	268,032us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingAndBuildingImprovementsMember
Machinery and Equipment [Member]
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	530,332us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_MachineryAndEquipmentMember	529,358us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_MachineryAndEquipmentMember
Vehicles [Member]
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	13,581us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_VehiclesMember	13,799us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_VehiclesMember
Office Equipment [Member]
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	19,363us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_OfficeEquipmentMember	19,260us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_OfficeEquipmentMember
Land Improvements [Member]
Property, plant, equipment, and mineral properties
Property, Plant and Equipment, Gross	74,636us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandImprovementsMember	73,933us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandImprovementsMember
Land [Member]
Property, plant, equipment, and mineral properties
Land	909us-gaap_Land / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandMember	909us-gaap_Land / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandMember
Construction in Progress [Member]
Property, plant, equipment, and mineral properties
Construction in Progress, Gross	$ 6,812us-gaap_ConstructionInProgressGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_ConstructionInProgressMember	$ 5,600us-gaap_ConstructionInProgressGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_ConstructionInProgressMember

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Mineral properties and development costs which include acquisition costs, the cost of drilling wells, and the cost of other development work, net of depletion.

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Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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