v2.4.1.9
Significant Agreements Litigation Settlement (Details) (Past Infringement [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended 3 Months Ended
Dec. 31, 2013
Jun. 30, 2013
Dec. 31, 2013
Sep. 30, 2013
Litigation Settlement, Amount $ 36.4us-gaap_LitigationSettlementAmount      
Pegatron [Member]
        
Litigation Settlement, Amount   23.5us-gaap_LitigationSettlementAmount
/ us-gaap_MajorCustomersAxis
= idcc_PegatronMember
/ idcc_RoyaltyRevenueAxis
= idcc_PastInfringementMember		 71.4us-gaap_LitigationSettlementAmount
/ us-gaap_MajorCustomersAxis
= idcc_PegatronMember
/ idcc_RoyaltyRevenueAxis
= idcc_PastInfringementMember		  
Technology Solutions Customer [Member]
        
Litigation Settlement, Amount     $ 53.3us-gaap_LitigationSettlementAmount
/ us-gaap_MajorCustomersAxis
= idcc_TechnologySolutionsCustomerMember
/ idcc_RoyaltyRevenueAxis
= idcc_PastInfringementMember		 $ 51.6us-gaap_LitigationSettlementAmount
/ us-gaap_MajorCustomersAxis
= idcc_TechnologySolutionsCustomerMember
/ idcc_RoyaltyRevenueAxis
= idcc_PastInfringementMember