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Summary of Significant Accounting Policies Fair Value Measurements (Details) (USD $)
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12 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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Jun. 30, 2014
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Concentration Risk, Additional Characteristic |
three |
five |
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| Concentration Risk, Percentage |
94.00%us-gaap_ConcentrationRiskPercentage1 |
96.00%us-gaap_ConcentrationRiskPercentage1 |
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| Assets, Fair Value Disclosure, Recurring |
$ 703,928,000us-gaap_AssetsFairValueDisclosureRecurring |
$ 698,451,000us-gaap_AssetsFairValueDisclosureRecurring |
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| Commercial Paper |
120,600,000us-gaap_CommercialPaper |
32,000,000us-gaap_CommercialPaper |
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| Long-term Debt, Excluding Current Maturities |
217,835,000us-gaap_LongTermDebtNoncurrent |
208,813,000us-gaap_LongTermDebtNoncurrent |
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| Long-term Debt, Fair Value |
255,300,000us-gaap_LongTermDebtFairValue |
234,000,000us-gaap_LongTermDebtFairValue |
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| Investment Owned, at Fair Value |
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64,300,000us-gaap_IntangibleAssetsGrossExcludingGoodwill |
| Money Market Funds and Demand Deposits [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
307,995,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember |
465,722,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember |
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| Commercial Paper [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
207,449,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember |
192,478,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember |
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| US Treasury and Government [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
151,618,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember |
31,688,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember |
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| Corporate Bonds and Asset Backed Securities [Domain] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
36,866,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_CorporateBondsAndAssetBackedSecuritiesDomain |
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| Corporate Bond Securities [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
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8,563,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CorporateBondSecuritiesMember |
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| Fair Value, Inputs, Level 1 [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
308,666,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
467,120,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 1 [Member] | Money Market Funds and Demand Deposits [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
307,995,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
465,722,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 1 [Member] | Corporate Bonds and Asset Backed Securities [Domain] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
671,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_CorporateBondsAndAssetBackedSecuritiesDomain / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
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1,398,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
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| Fair Value, Inputs, Level 2 [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
395,262,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
231,331,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 2 [Member] | Money Market Funds and Demand Deposits [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
207,449,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
192,478,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
151,618,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
31,688,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 2 [Member] | Corporate Bonds and Asset Backed Securities [Domain] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
36,195,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_CorporateBondsAndAssetBackedSecuritiesDomain / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
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7,165,000us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |
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| Fair Value, Inputs, Level 3 [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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| Fair Value, Inputs, Level 3 [Member] | Money Market Funds and Demand Deposits [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_MoneyMarketFundsAndDemandDepositsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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| Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CommercialPaperMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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| Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_USTreasuryAndGovernmentMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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| Fair Value, Inputs, Level 3 [Member] | Corporate Bonds and Asset Backed Securities [Domain] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = idcc_CorporateBondsAndAssetBackedSecuritiesDomain / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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| Fair Value, Inputs, Level 3 [Member] | Corporate Bond Securities [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Assets, Fair Value Disclosure, Recurring |
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$ 0us-gaap_AssetsFairValueDisclosureRecurring / us-gaap_FairValueByAssetClassAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |
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