Option Activity (Detail) (Qunar, USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Qunar
Share Option Roll Forward - Number of shares
Outstanding, December 31, 2013	25,192,696
Granted	9,993,411
Exercised	(8,907,408)
Forfeited/Cancelled	(1,115,256)
Outstanding, December 31, 2014	25,163,443	25,192,696
Vested and expected to vest at December 31, 2014	21,880,749
Exercisable at December 31, 2014	9,685,685
Share Option Roll Forward - Weighted-Average Exercise Price
Outstanding, December 31, 2013	$ 1.40
Granted	$ 0.01
Exercised	$ 0.27
Forfeited/Cancelled	$ 0.02
Outstanding, December 31, 2014	$ 1.30	$ 1.40
Vested and expected to vest at December 31, 2014	$ 1.43
Exercisable at December 31, 2014	$ 1.72
Share Option Roll Forward - Weighted-Average Remaining Contractual Life (in years)
Outstanding, December 31, 2013	7 years 10 months 21 days	7 years 4 months 21 days
Vested and expected to vest at December 31, 2014	7 years 9 months
Exercisable at December 31, 2014	6 years 7 months 13 days
Share Option Roll Forward - Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2013	$ 184,355
Outstanding, December 31, 2014	201,417	184,355
Vested and expected to vest at December 31, 2014	176,072
Exercisable at December 31, 2014	$ 75,118

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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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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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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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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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