v2.4.1.9

Summary of Significant Accounting Policies Deferred Charges (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred Charges [Line Items]
Payments for Commissions	$ 300,000us-gaap_PaymentsForCommissions	$ 100,000us-gaap_PaymentsForCommissions	$ 4,700,000us-gaap_PaymentsForCommissions
Contract Revenue Cost	100,000us-gaap_ContractRevenueCost	100,000us-gaap_ContractRevenueCost	100,000us-gaap_ContractRevenueCost
Sales Commissions and Fees	400,000us-gaap_SalesCommissionsAndFees	300,000us-gaap_SalesCommissionsAndFees	5,000,000us-gaap_SalesCommissionsAndFees
Amortization of Financing Costs	1,303,000us-gaap_AmortizationOfFinancingCosts	1,303,000us-gaap_AmortizationOfFinancingCosts	1,303,000us-gaap_AmortizationOfFinancingCosts
Deferred Sales Commission Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net	342,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredSalesCommissionCurrentMember	290,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredSalesCommissionCurrentMember
Deferred Contract Revenue Costs Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net	79,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredContractRevenueCostsCurrentMember	79,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredContractRevenueCostsCurrentMember
Deferred Finance Costs Current [Member]
Deferred Charges [Line Items]
Deferred Finance Costs, Net	1,303,000us-gaap_DeferredFinanceCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredFinanceCostsCurrentMember	1,303,000us-gaap_DeferredFinanceCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredFinanceCostsCurrentMember
Deferred Sales Commission Non-Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net	495,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredSalesCommissionNonCurrentMember	750,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredSalesCommissionNonCurrentMember
Deferred Contract Revenue Costs Non-Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net	79,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredContractRevenueCostsNonCurrentMember	158,000us-gaap_OtherDeferredCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredContractRevenueCostsNonCurrentMember
Deferred Finance Costs Non-Current [Member]
Deferred Charges [Line Items]
Deferred Finance Costs, Net	326,000us-gaap_DeferredFinanceCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredFinanceCostsNonCurrentMember	1,629,000us-gaap_DeferredFinanceCostsNet / us-gaap_StatementScenarioAxis = idcc_DeferredFinanceCostsNonCurrentMember
Convertible Debt [Member] | Equity [Member]
Deferred Charges [Line Items]
Payments of Debt Issuance Costs				$ 1,500,000us-gaap_PaymentsOfDebtIssuanceCosts / us-gaap_BalanceSheetLocationAxis = us-gaap_EquityMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember

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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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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 45

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Costs incurred and are directly related to generating contract revenues.

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Net amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies.

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The amount of cash paid for commissions during the current period.

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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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