v2.4.1.9

Selected Quarterly Results (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effect of Fourth Quarter Events [Line Items]
Restructuring Charges								$ 1,500,000us-gaap_RestructuringCharges	$ 0us-gaap_RestructuringCharges	$ 1,544,000us-gaap_RestructuringCharges	$ 12,536,000us-gaap_RestructuringCharges
Other than Temporary Impairment Losses, Investments					15,000,000us-gaap_ImpairmentOfInvestments			6,700,000us-gaap_ImpairmentOfInvestments	559,000us-gaap_ImpairmentOfInvestments	21,720,000us-gaap_ImpairmentOfInvestments	0us-gaap_ImpairmentOfInvestments
Sales Revenue, Goods, Net									1,999,000us-gaap_SalesRevenueGoodsNet	0us-gaap_SalesRevenueGoodsNet	384,000,000us-gaap_SalesRevenueGoodsNet
Revenues	86,121,000us-gaap_Revenues	77,622,000us-gaap_Revenues	194,234,000us-gaap_Revenues	57,844,000us-gaap_Revenues	99,683,000us-gaap_Revenues	110,623,000us-gaap_Revenues	67,692,000us-gaap_Revenues	47,363,000us-gaap_Revenues	415,821,000us-gaap_Revenues	325,361,000us-gaap_Revenues	663,063,000us-gaap_Revenues
NET INCOME	13,790,000us-gaap_NetIncomeLoss	13,512,000us-gaap_NetIncomeLoss	78,901,000us-gaap_NetIncomeLoss	(1,861,000)us-gaap_NetIncomeLoss	14,536,000us-gaap_NetIncomeLoss	26,660,000us-gaap_NetIncomeLoss	9,238,000us-gaap_NetIncomeLoss	(12,269,000)us-gaap_NetIncomeLoss	101,420,000us-gaap_NetIncomeLoss	35,683,000us-gaap_NetIncomeLoss	271,804,000us-gaap_NetIncomeLoss
NET INCOME PER COMMON SHARE — BASIC	$ 0.37us-gaap_EarningsPerShareBasic	$ 0.34us-gaap_EarningsPerShareBasic	$ 1.95us-gaap_EarningsPerShareBasic	$ (0.05)us-gaap_EarningsPerShareBasic	$ 0.35us-gaap_EarningsPerShareBasic	$ 0.65us-gaap_EarningsPerShareBasic	$ 0.22us-gaap_EarningsPerShareBasic	$ (0.30)us-gaap_EarningsPerShareBasic	$ 2.65us-gaap_EarningsPerShareBasic	$ 0.93us-gaap_EarningsPerShareBasic	$ 6.31us-gaap_EarningsPerShareBasic
NET INCOME PER COMMON SHARE — DILUTED	$ 0.36us-gaap_EarningsPerShareDiluted	$ 0.34us-gaap_EarningsPerShareDiluted	$ 1.93us-gaap_EarningsPerShareDiluted	$ (0.05)us-gaap_EarningsPerShareDiluted	$ 0.35us-gaap_EarningsPerShareDiluted	$ 0.64us-gaap_EarningsPerShareDiluted	$ 0.22us-gaap_EarningsPerShareDiluted	$ (0.30)us-gaap_EarningsPerShareDiluted	$ 2.62us-gaap_EarningsPerShareDiluted	$ 0.92us-gaap_EarningsPerShareDiluted	$ 6.26us-gaap_EarningsPerShareDiluted
Past Infringement [Member]
Effect of Fourth Quarter Events [Line Items]
Royalty Revenue			119,900,000us-gaap_RoyaltyRevenue / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember
Litigation Settlement, Amount					36,400,000us-gaap_LitigationSettlementAmount / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember
Pegatron [Member] | Past Infringement [Member]
Effect of Fourth Quarter Events [Line Items]
Litigation Settlement, Amount							23,500,000us-gaap_LitigationSettlementAmount / us-gaap_MajorCustomersAxis = idcc_PegatronMember / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember			71,400,000us-gaap_LitigationSettlementAmount / us-gaap_MajorCustomersAxis = idcc_PegatronMember / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember
Technology Solutions Customer [Member] | Past Infringement [Member]
Effect of Fourth Quarter Events [Line Items]
Litigation Settlement, Amount						$ 51,600,000us-gaap_LitigationSettlementAmount / us-gaap_MajorCustomersAxis = idcc_TechnologySolutionsCustomerMember / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember				$ 53,300,000us-gaap_LitigationSettlementAmount / us-gaap_MajorCustomersAxis = idcc_TechnologySolutionsCustomerMember / idcc_RoyaltyRevenueAxis = idcc_PastInfringementMember

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