v2.4.1.9
Property and Equipment (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Property, Plant and Equipment [Line Items]      
Land $ 695,000us-gaap_Land $ 695,000us-gaap_Land  
Building and improvements 11,076,000us-gaap_BuildingsAndImprovementsGross 7,902,000us-gaap_BuildingsAndImprovementsGross  
Engineering and test equipment 11,970,000us-gaap_MachineryAndEquipmentGross 11,631,000us-gaap_MachineryAndEquipmentGross  
Computer Equipment And Software Gross 27,678,000idcc_ComputerEquipmentAndSoftwareGross 25,368,000idcc_ComputerEquipmentAndSoftwareGross  
Furniture and fixtures 1,292,000us-gaap_FurnitureAndFixturesGross 1,166,000us-gaap_FurnitureAndFixturesGross  
Leasehold improvements 7,406,000us-gaap_LeaseholdImprovementsGross 6,477,000us-gaap_LeaseholdImprovementsGross  
Property and equipment, gross 60,117,000us-gaap_PropertyPlantAndEquipmentGross 53,239,000us-gaap_PropertyPlantAndEquipmentGross  
Less: accumulated depreciation (47,571,000)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment (43,704,000)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment  
Property and equipment, net 12,546,000us-gaap_PropertyPlantAndEquipmentNet 9,535,000us-gaap_PropertyPlantAndEquipmentNet  
Depreciation 3,900,000us-gaap_Depreciation 3,600,000us-gaap_Depreciation 3,600,000us-gaap_Depreciation
Capitalized Computer Software, Amortization 1,400,000us-gaap_CapitalizedComputerSoftwareAmortization 1,000,000us-gaap_CapitalizedComputerSoftwareAmortization 1,000,000us-gaap_CapitalizedComputerSoftwareAmortization
Capitalized Computer Software, Accumulated Amortization 14,300,000us-gaap_CapitalizedComputerSoftwareAccumulatedAmortization 12,700,000us-gaap_CapitalizedComputerSoftwareAccumulatedAmortization  
Capitalized Computer Software, Net $ 2,200,000us-gaap_CapitalizedComputerSoftwareNet $ 2,500,000us-gaap_CapitalizedComputerSoftwareNet