| Schedule of Stockholders Equity [Table Text Block] |
Changes in shareholders’ equity for the six months ended June 30, 2015 and June 30, 2014 were as follows (in thousands): | | | | | | | | | | For the Six Months Ended June 30, | | 2015 | | 2014 | Balance beginning of period, December 31 | $ | 468,328 |
| | $ | 528,650 |
| Net income attributable to InterDigital, Inc. | 61,667 |
| | 77,040 |
| Unrealized gain on investments, net | 8 |
| | 382 |
| Cash dividends declared | (14,475 | ) | | (11,987 | ) | Repurchase of Common Stock | (70,572 | ) | | (8,454 | ) | Convertible note hedge transactions, net of tax | (38,594 | ) | | — |
| Warrant transactions | 42,881 |
| | — |
| Equity component of the 2020 Notes, net of tax | 38,567 |
| | — |
| Deferred financing costs allocated to equity | (2,430 | ) | | — |
| Exercise of common stock options | 26 |
| | 353 |
| Taxes withheld upon restricted stock unit vestings | (9,557 | ) | | (2,814 | ) | Tax benefit from share-based compensation | 2,163 |
| | 1,196 |
| Share-based compensation | 6,299 |
| | 9,721 |
| Total InterDigital, Inc. shareholders’ equity end of period | $ | 484,311 |
| | $ | 594,087 |
| Noncontrolling Interest Balance beginning of period, December 31 | 7,349 |
| | 5,170 |
| Proceeds from noncontrolling interests | 2,551 |
| | 2,550 |
| Net loss attributable to noncontrolling interest | (1,380 | ) | | (1,483 | ) | Noncontrolling interest | 8,520 |
| | 6,237 |
| Total Equity end of period | $ | 492,831 |
| | $ | 600,324 |
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