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Share-Based Compensation - Schedule of Estimated Fair Value of Share-Based Awards on Respective Grant Dates using Binomial Option Pricing Model (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value of ordinary share $ 36.62us-gaap_SharePrice   $ 3.70us-gaap_SharePrice
Risk-free interest rates 2.909%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate   1.73%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Risk-free interest rates, Minimum   2.07%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum  
Risk-free interest rates, Maximum   2.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum  
Expected exercise multiple $ 2.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice $ 2.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice $ 2.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice
Expected volatility 53.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate   60.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Expected volatility, Minimum   53.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum  
Expected volatility, Maximum   55.49%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum  
Expected dividend yield 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Weighted average fair value per option granted $ 34.57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue   $ 2.36us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value of ordinary share   $ 4.58us-gaap_SharePrice
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Weighted average fair value per option granted $ 34.52us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
$ 3.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value of ordinary share   $ 11.64us-gaap_SharePrice
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Weighted average fair value per option granted $ 34.59us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
$ 9.69us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RangeAxis
= us-gaap_MaximumMember