Share-based Compensation (Share Option Activities) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014 years	Dec. 31, 2013 years	Dec. 31, 2012 years
Number of Options
Number of Options, Outstanding, Beginning Balance	39,770,121	13,997,069	19,341,696
Number of Options, Granted	21,052,758	30,732,900	0
Number of Options, Forfeited and expired	(4,013,850)	(1,408,938)	(456,870)
Number of Options, Exercised	(6,542,022)	(3,550,910)	(4,887,757)
Number of Options, Outstanding, Ending Balance	50,267,007	39,770,121	13,997,069
Number of Options, Exercisable	13,382,374
Number of Options, Vested and expected to vest	43,222,033
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding, Beginning Balance (US$ per share)	$ 0.44	$ 0.03	$ 0.03
Weighted Average Exercise Price, Granted (US$ per share)	$ 1.30	$ 0.58	$ 0.00
Weighted Average Exercise Price, Forfeited and expired (US$ per share)	$ 0.91	$ 0.44	$ 0.03
Weighted Average Exercise Price, Exercised (US$ per share)	$ 0.23	$ 0.03	$ 0.03
Weighted Average Exercise Price, Outstanding, Ending Balance (US$ per share)	$ 0.79	$ 0.44	$ 0.03
Weighted Average Exercise Price, Exercisable (US$ per share)	$ 0.30
Weighted Average Exercise Price, Vested and expected to vest (US$ per share)	$ 0.76
Weighted Average Remaining Contractual Life
Weighted Average Remaining Contractual Life, Outstanding, Beginning Balance (in years)	8.1	5.4	6.4
Weighted Average Remaining Contractual Life, Outstanding, Ending Balance (in years)	8.2	8.1	5.4
Weighted Average Remaining Contractual Life, Exercisable (in years)	5.8
Weighted Average Remaining Contractual Life, Vested and expected to vest (in years)	8.0
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding, Beginning Balance (US$ in million)	$ 30.2	$ 5.9	$ 13.0
Aggregate Intrinsic Value, Exercised (US$ in million)	7.1	3.6	3.1
Aggregate Intrinsic Value, Outstanding, Ending Balance (US$ in million)	17.6	30.2	5.9
Aggregate Intrinsic Value, Exercisable (US$ in million)	10.0
Aggregate Intrinsic Value, Vested and expected to vest (US$ in million)	$ 16.2

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Weighted average remaining contractual term for option awards outstanding.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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