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