v2.4.1.9

Obligations Senior Convertible Note, Note Hedge and Warrant Transaction (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 24, 2012	Mar. 31, 2011	Dec. 31, 2011	Apr. 04, 2011	Mar. 29, 2011	Mar. 30, 2011
Debt Instrument [Line Items]
Senior Notes	$ 230,000,000us-gaap_SeniorNotes	$ 230,000,000us-gaap_SeniorNotes					$ 230,000,000us-gaap_SeniorNotes
Debt Instrument, Interest Rate, Effective Percentage							7.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage
Interest Expense, Debt, Excluding Amortization	5,750,000us-gaap_InterestExpenseDebtExcludingAmortization	5,750,000us-gaap_InterestExpenseDebtExcludingAmortization	5,750,000us-gaap_InterestExpenseDebtExcludingAmortization
Accretion of debt discount	(9,022,000)us-gaap_AccretionExpense	(8,423,000)us-gaap_AccretionExpense	(7,862,000)us-gaap_AccretionExpense
Amortization of Financing Costs	1,303,000us-gaap_AmortizationOfFinancingCosts	1,303,000us-gaap_AmortizationOfFinancingCosts	1,303,000us-gaap_AmortizationOfFinancingCosts
Senior Convertible Note, Note Hedge, and Warrant Transaction Interest Expense	16,075,000idcc_SeniorConvertibleNoteNoteHedgeAndWarrantTransactionInterestExpense	15,476,000idcc_SeniorConvertibleNoteNoteHedgeAndWarrantTransactionInterestExpense	14,915,000idcc_SeniorConvertibleNoteNoteHedgeAndWarrantTransactionInterestExpense
Convertible Note Hedge 1 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities				37,100,000us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNoteHedge1Member
Convertible Note Hedge 2 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities				5,600,000us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNoteHedge2Member
Convertible Note Hedge [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities				42,700,000us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNoteHedgeMember
Convertible Note/ Hedge Warrant, net [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities			10,900,000us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNoteHedgeWarrantNetMember
Note Warrant [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants					27,600,000us-gaap_ProceedsFromIssuanceOfWarrants / us-gaap_DebtInstrumentAxis = us-gaap_NoteWarrantMember
Note Warrant2 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants					4,100,000us-gaap_ProceedsFromIssuanceOfWarrants / us-gaap_DebtInstrumentAxis = idcc_NoteWarrant2Member
Convertible Debt [Member] | Convertible Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage							2.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNotes2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Debt Instrument, Convertible, Conversion Ratio			17.958us-gaap_DebtInstrumentConvertibleConversionRatio1 / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNotes2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Debt Conversion, Converted Instrument, Amount			1,000us-gaap_DebtConversionConvertedInstrumentAmount1 / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNotes2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Debt Instrument, Convertible, Conversion Price							$ 55.69us-gaap_DebtInstrumentConvertibleConversionPrice1 / us-gaap_DebtInstrumentAxis = idcc_ConvertibleNotes2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Convertible Debt 1 [Member]
Debt Instrument [Line Items]
Senior Notes								200,000,000us-gaap_SeniorNotes / us-gaap_LongtermDebtTypeAxis = idcc_ConvertibleDebt1Member
Convertible Note Overallotment [Member]
Debt Instrument [Line Items]
Senior Notes								30,000,000us-gaap_SeniorNotes / us-gaap_LongtermDebtTypeAxis = idcc_ConvertibleNoteOverallotmentMember
Equity [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Class of Warrant or Right, Outstanding								3,500us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember	500us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Derivative, Price Risk Option Strike Price								64.0909us-gaap_DerivativePriceRiskOptionStrikePrice / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Senior Notes							43,000,000us-gaap_SeniorNotes / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Senior Convertible Notes [Equity net of tax]							28,000,000idcc_SeniorConvertibleNotesEquityNetOfTax / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Payments of Debt Issuance Costs						1,500,000us-gaap_PaymentsOfDebtIssuanceCosts / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
other long-term assets [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs						6,500,000us-gaap_PaymentsOfDebtIssuanceCosts / us-gaap_BalanceSheetLocationAxis = idcc_OtherLongTermAssetsMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember
Other Long-term Liabilities [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes							$ 187,000,000us-gaap_SeniorNotes / us-gaap_BalanceSheetLocationAxis = idcc_OtherLongTermLiabilitiesMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember

X

- Definition

The component of interest expense comprised of the following: 1) Coupon Interest - interest expense charge for contractual coupon interest due on face value of the Senior Convertible Note 2) Accretion of Debt Discount - amortization of Original Issue Discount (which is charged to interest expense) on the Senior Convertible Note over the life of the Note, and 3) Amortization of Deferred Financing Costs - periodic charge against earnings over the life of the financing arrangement to which such costs relate.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders. Convertible notes can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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Number of warrants or rights outstanding.

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The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The price per share of the conversion feature embedded in the debt instrument.

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Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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The strike price on the price risk option contract such as a put option or a call option.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).

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The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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