v2.4.1.9
Summary of Significant Accounting Policies Income Tax (Details) (USD $)
12 Months Ended 108 Months Ended 96 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Income Tax Contingency [Line Items]          
Income taxes paid, including foreign witholding taxes $ 114,876,000us-gaap_IncomeTaxesPaid $ 24,961,000us-gaap_IncomeTaxesPaid $ 116,871,000us-gaap_IncomeTaxesPaid    
Income Tax Expense (Benefit) 52,108,000us-gaap_IncomeTaxExpenseBenefit 25,836,000us-gaap_IncomeTaxExpenseBenefit 136,830,000us-gaap_IncomeTaxExpenseBenefit    
Unrecognized Tax Benefits 5,700,000us-gaap_ForeignIncomeTaxExpenseBenefitContinuingOperations        
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions 1,266,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions    
Unrecognized Tax Benefits 5,700,000us-gaap_TaxCreditCarryforwardAmount     5,700,000us-gaap_TaxCreditCarryforwardAmount  
Unrecognized Tax Benefits, Period Increase (Decrease) 700,000us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease        
Foreign Tax Authority [Member]          
Income Tax Contingency [Line Items]          
Income taxes paid, including foreign witholding taxes 70,700,000us-gaap_IncomeTaxesPaid
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ForeignCountryMember
23,300,000us-gaap_IncomeTaxesPaid
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ForeignCountryMember
3,600,000us-gaap_IncomeTaxesPaid
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ForeignCountryMember
239,800,000us-gaap_IncomeTaxesPaid
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ForeignCountryMember
 
Foreign Tax Authority [Member] | Tax Period 2006-2013 [Member] [Domain]          
Income Tax Contingency [Line Items]          
Income taxes paid, including foreign witholding taxes         239,800,000us-gaap_IncomeTaxesPaid
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ForeignCountryMember
/ us-gaap_TaxPeriodAxis
= idcc_TaxPeriod20062013MemberDomain
Research and Development Arrangement [Member]          
Income Tax Contingency [Line Items]          
Income Tax Expense (Benefit) $ 900,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_ResearchAndDevelopmentArrangementMember