| Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] |
NET INCOME PER SHARE: Basic Earnings Per Share ("EPS") is calculated by dividing net income available to common shareholders by the weighted-average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if options or other securities with features that could result in the issuance of common stock were exercised or converted to common stock. The following tables reconcile the numerator and the denominator of the basic and diluted net income per share computation (in thousands, except for per share data): | | | | | | | | | | | | | | | | | | For the Three Months Ended June 30, | | 2015 | | 2014 | | Basic | | Diluted | | Basic | | Diluted | Numerator: | | | | | | | | Net income applicable to InterDigital, Inc. | $ | 32,602 |
| | $ | 32,602 |
| | $ | 78,901 |
| | $ | 78,901 |
| Denominator: | | | | | | | | Weighted-average shares outstanding: Basic | 36,022 |
| | 36,022 |
| | 40,443 |
| | 40,443 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | 420 |
| | | | 379 |
| Weighted-average shares outstanding: Diluted | | | 36,442 |
| | | | 40,822 |
| Earnings Per Share: | | | | | | | | Net income: Basic | $ | 0.91 |
| | $ | 0.91 |
| | $ | 1.95 |
| | $ | 1.95 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | (0.02 | ) | | | | (0.02 | ) | Net income: Diluted | | | $ | 0.89 |
| | | | $ | 1.93 |
|
| | | | | | | | | | | | | | | | | | For the Six Months Ended June 30, | | 2015 | | 2014 | | Basic | | Diluted | | Basic | | Diluted | Numerator: | | | | | | | | Net income applicable to InterDigital, Inc. | $ | 61,667 |
| | $ | 61,667 |
| | $ | 77,040 |
| | $ | 77,040 |
| Denominator: | | | | | | | | Weighted-average shares outstanding: Basic | 36,486 |
| | 36,486 |
| | 40,444 |
| | 40,444 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | 397 |
| | | | 199 |
| Weighted-average shares outstanding: Diluted | | | 36,883 |
| | | | 40,643 |
| Earnings Per Share: | | | | | | | | Net income: Basic | $ | 1.69 |
| | $ | 1.69 |
| | $ | 1.90 |
| | $ | 1.90 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | (0.02 | ) | | | | — |
| Net income: Diluted | | | $ | 1.67 |
| | | | $ | 1.90 |
|
Certain shares of common stock issuable upon the exercise or conversion of certain securities have been excluded from our computation of earnings per share because the strike price or conversion rate, as applicable, of such securities was less than the average market price of our common stock for the three and/or six month periods ended June 30, 2015 and/or June 30, 2014, as applicable, and, as a result, the effect of such exercise or conversion would have been anti-dilutive. Set forth below are the securities and the weighted average number of shares of common stock underlying such securities that were excluded from our computation of earnings per share for the periods presented (in thousands): | | | | | | | | | | | | | | | | For the Three Months Ended June 30, | | For the Six Months Ended June 30, | | | 2015 | | 2014 | | 2015 | | 2014 | Restricted Stock Units | | — |
| | 10 |
| | 2 |
| | 3 |
| Stock options | | 94 |
| | 213 |
| | 56 |
| | 160 |
| Convertible securities | | 4,366 |
| | 4,130 |
| | 6,803 |
| | 4,130 |
| Warrants | | 8,496 |
| | 4,130 |
| | 6,808 |
| | 4,130 |
| Total | | 12,956 |
| | 8,483 |
| | 13,669 |
| | 8,423 |
|
| | | | | | | | | | | | | | | | | | For the Three Months Ended June 30, | | 2015 | | 2014 | | Basic | | Diluted | | Basic | | Diluted | Numerator: | | | | | | | | Net income applicable to InterDigital, Inc. | $ | 32,602 |
| | $ | 32,602 |
| | $ | 78,901 |
| | $ | 78,901 |
| Denominator: | | | | | | | | Weighted-average shares outstanding: Basic | 36,022 |
| | 36,022 |
| | 40,443 |
| | 40,443 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | 420 |
| | | | 379 |
| Weighted-average shares outstanding: Diluted | | | 36,442 |
| | | | 40,822 |
| Earnings Per Share: | | | | | | | | Net income: Basic | $ | 0.91 |
| | $ | 0.91 |
| | $ | 1.95 |
| | $ | 1.95 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | (0.02 | ) | | | | (0.02 | ) | Net income: Diluted | | | $ | 0.89 |
| | | | $ | 1.93 |
|
| | | | | | | | | | | | | | | | | | For the Six Months Ended June 30, | | 2015 | | 2014 | | Basic | | Diluted | | Basic | | Diluted | Numerator: | | | | | | | | Net income applicable to InterDigital, Inc. | $ | 61,667 |
| | $ | 61,667 |
| | $ | 77,040 |
| | $ | 77,040 |
| Denominator: | | | | | | | | Weighted-average shares outstanding: Basic | 36,486 |
| | 36,486 |
| | 40,444 |
| | 40,444 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | 397 |
| | | | 199 |
| Weighted-average shares outstanding: Diluted | | | 36,883 |
| | | | 40,643 |
| Earnings Per Share: | | | | | | | | Net income: Basic | $ | 1.69 |
| | $ | 1.69 |
| | $ | 1.90 |
| | $ | 1.90 |
| Dilutive effect of stock options, RSUs, convertible securities, and warrants | | | (0.02 | ) | | | | — |
| Net income: Diluted | | | $ | 1.67 |
| | | | $ | 1.90 |
|
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