Significant Agreements	12 Months Ended
Dec. 31, 2014
Variable Interest Entity [Line Items]
Legal Matters and Contingencies [Text Block]	SIGNIFICANT EVENTS Patent License Agreements During second quarter 2014, we entered into a patent license agreement with Samsung Electronics Co., Ltd. ("Samsung"). The multi-year agreement also resolved all pending litigation between the companies. The royalty-bearing license agreement sets forth terms covering the sale by Samsung of 3G, 4G and certain future generation wireless products. The agreement provides Samsung the ability to terminate certain rights and obligations under the license for the period after 2017 but has the potential to provide a license to Samsung for a total of ten years, including 2013. For the period through the earlier of any exercise or expiration of Samsung’s termination right, we expect to recognize revenue associated with this agreement on a straight-line basis. The amount of revenue we will recognize after 2017 will depend on, among other things, whether or not Samsung elects to terminate certain rights and obligations under the license and amounts payable in 2017 and thereafter. During 2014 , we recognized $138.0 million of revenue, including $86.2 million of past patent royalties and $51.8 million of recurring fixed-fee royalties, associated with this agreement. Additionally, during second quarter 2014, the company’s patent-holding subsidiaries entered into patent license agreements with two additional licensees. Both of these agreements cover infrastructure equipment and one of the agreements also covers terminal units. We recognized past sales from each agreement in second quarter 2014 and are recognizing future revenue from these agreements on a straight-line basis over their respective expected terms, beginning with second quarter 2014. These two agreements contributed $48.1 million of revenue in the year, including $16.0 million of recurring revenue and $32.1 million of past sales. A portion of the consideration received under these agreements was in the form of patents. Refer to Note 2, "Summary of Significant Accounting Policies," for additional information related to the estimates and methods used to determine the fair value of the patents acquired. Each of the three patent license agreements signed during second quarter 2014, as discussed above, is a multiple-element arrangement for accounting purposes. Consistent with the revenue recognition policy disclosed in Note 2, "Summary of Significant Accounting Policies," for each agreement, we identified each element of the arrangement, estimated its relative value for purposes of allocating the arrangement consideration and determined when each of those elements should be recognized. Using the accounting guidance applicable to multiple-element revenue arrangements, we allocated the consideration to each element for accounting purposes using our best estimate of the term and value of each element. The development of a number of these inputs and assumptions in the model requires a significant amount of management judgment and is based upon a number of factors, including the assumed royalty rates, sales volumes, discount rate and other relevant factors. Changes in any of a number of these assumptions could have had a substantial impact on the relative fair value assigned to each element for accounting purposes. These inputs and assumptions represent management's best estimates at the time of the transactions. Huawei Settlement Agreement On December 23, 2013, InterDigital and Huawei reached a settlement agreement to enter into binding arbitration to resolve their global patent licensing dispute. The agreement is based on an expedited process leading to a license on terms set by the arbitration panel, with the arbitration process expected to be completed in 2015.

SIGNIFICANT EVENTS

Patent License Agreements

During second quarter 2014, we entered into a patent license agreement with Samsung Electronics Co., Ltd. ("Samsung"). The multi-year agreement also resolved all pending litigation between the companies. The royalty-bearing license agreement sets forth terms covering the sale by Samsung of 3G, 4G and certain future generation wireless products. The agreement provides Samsung the ability to terminate certain rights and obligations under the license for the period after 2017 but has the potential to provide a license to Samsung for a total of ten years, including 2013. For the period through the earlier of any exercise or expiration of Samsung’s termination right, we expect to recognize revenue associated with this agreement on a straight-line basis. The amount of revenue we will recognize after 2017 will depend on, among other things, whether or not Samsung elects to terminate certain rights and obligations under the license and amounts payable in 2017 and thereafter. During 2014 , we recognized $138.0 million of revenue, including $86.2 million of past patent royalties and $51.8 million of recurring fixed-fee royalties, associated with this agreement.

Additionally, during second quarter 2014, the company’s patent-holding subsidiaries entered into patent license agreements with two additional licensees. Both of these agreements cover infrastructure equipment and one of the agreements also covers terminal units. We recognized past sales from each agreement in second quarter 2014 and are recognizing future revenue from these agreements on a straight-line basis over their respective expected terms, beginning with second quarter 2014. These two agreements contributed $48.1 million of revenue in the year, including $16.0 million of recurring revenue and $32.1 million of past sales. A portion of the consideration received under these agreements was in the form of patents. Refer to Note 2, "Summary of Significant Accounting Policies," for additional information related to the estimates and methods used to determine the fair value of the patents acquired.

Each of the three patent license agreements signed during second quarter 2014, as discussed above, is a multiple-element arrangement for accounting purposes. Consistent with the revenue recognition policy disclosed in Note 2, "Summary of Significant Accounting Policies," for each agreement, we identified each element of the arrangement, estimated its relative value for purposes of allocating the arrangement consideration and determined when each of those elements should be recognized. Using the accounting guidance applicable to multiple-element revenue arrangements, we allocated the consideration to each element for accounting purposes using our best estimate of the term and value of each element. The development of a number of these inputs and assumptions in the model requires a significant amount of management judgment and is based upon a number of factors, including the assumed royalty rates, sales volumes, discount rate and other relevant factors. Changes in any of a number of these assumptions could have had a substantial impact on the relative fair value assigned to each element for accounting purposes. These inputs and assumptions represent management's best estimates at the time of the transactions.

Huawei Settlement Agreement

On December 23, 2013, InterDigital and Huawei reached a settlement agreement to enter into binding arbitration to resolve their global patent licensing dispute. The agreement is based on an expedited process leading to a license on terms set by the arbitration panel, with the arbitration process expected to be completed in 2015.