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Share-Based Compensation - Additional Information (Detail)
3 Months Ended
Apr. 30, 2015
Stock Options  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock exercised 1,200,940us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Stock Appreciation Rights (SARs)  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock exercised 502,125us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_StockAppreciationRightsSARSMember
Performance Stock Units  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
stock units vested 251,081us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Restricted Stock Units (RSUs)  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
stock units vested 5,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember