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SHARE-BASED COMPENSATION (Summary of Share Options Granted to Both Employees and Non-employees) (Details) (Share options [Member], USD $)
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12 Months Ended |
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Dec. 31, 2014
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Share options [Member]
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| Number of Options |
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| Outstanding at the beginning of the period (in shares) |
29,920,388 |
| Options granted (in shares) |
3,475,132 |
| Options exercised (in shares) |
(10,372,019) |
| Options expired or cancelled (in shares) |
(950,230) |
| Options forfeited (in shares) |
(50,002) |
| Outstanding at the end of the period (in shares) |
22,023,269 |
| Vested and expected to vest at the end of the period (in shares) |
21,428,424 |
| Weighted-average exercise price |
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| Outstanding at the beginning of the period (in dollars per share) |
$ 0.40 |
| Options granted (in dollars per share) |
$ 1.33 |
| Options exercised (in dollars per share) |
$ 0.28 |
| Options expired or cancelled (in dollars per share) |
$ 0.52 |
| Options forfeited (in dollars per share) |
$ 1.85 |
| Outstanding at the end of the period (in dollars per share) |
$ 0.59 |
| Vested and expected to vest at the end of the period (in dollars per share) |
$ 0.59 |