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Employee Benefits and Stock-based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Jan. 31, 2015
Jan. 31, 2014
Jan. 31, 2013
Feb. 01, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Unvested early exercised options repurchased 86,925amba_ExercisedButUnvestedStockOptionsRepurchasedAsOfBalanceSheetDate 86,340amba_ExercisedButUnvestedStockOptionsRepurchasedAsOfBalanceSheetDate    
Closing price of ordinary shares 55.31amba_ClosingMarketPriceOfOrdinarySharesOnNASDAQOnLastDayOfReportingPeriod      
2012 Equity Incentive Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Voting power of all classes of company's shares 10.00%amba_VotingPowerOwnershipPercentage
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember		 10.00%amba_VotingPowerOwnershipPercentage
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember		 10.00%amba_VotingPowerOwnershipPercentage
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember		  
Additional ordinary shares reserved for issuance       1,297,555amba_NumberOfAdditionalSharesReservedEIP
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember
2012 Equity Incentive Plan [Member] | Scenario, plan automatically increased by the lessor of [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Annual increase in ordinary shares for available for future issuance       3,500,000amba_AnnualIncreaseInOrdinarySharesForAvailableForFutureIssuance
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioPlanMember
Annual shares increase for future issuance by percentage under 2012 equity plan       4.50%amba_AnnualIncreaseInSharesForAvailableForFutureIssuanceByPercentageOfOutstandingOrdinarySharesAsOfLastDayOfImmediatelyPrecedingFiscalYear
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEquityIncentivePlanMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioPlanMember
2012 Employee Stock Purchase Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Exercise price of stock options as percentage of fair market value at grant date 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		  
Percentage of salary contribution by employees 10.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		 10.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		 10.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember		  
Additional ordinary shares reserved for issuance       359,356amba_NumberOfAdditionalSharesReservedESPP
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember
2012 Employee Stock Purchase Plan [Member] | Scenario, plan automatically increased by the lessor of [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Annual increase in ordinary shares for available for future issuance       1,500,000amba_AnnualIncreaseInOrdinarySharesForAvailableForFutureIssuance
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioPlanMember
Annual shares increase for future issuance by percentage under 2012 employee stock purchase plan       1.25%amba_AnnualIncreaseInSharesForAvailableForFutureIssuanceByPercentageOfOutstandingOrdinarySharesOnFirstDayOfSuchFiscalYear
/ us-gaap_PlanNameAxis
= amba_TwoThousandTwelveEmployeeStockPurchasePlanMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioPlanMember
Stock options [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Total unrecognized compensation cost, stock options 10.3us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		      
Weighted average recognition period 2 years 4 months 21 days      
Stock options [Member] | 2012 Equity Incentive Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Option's term of up to 10 years from grant date 10 years 10 years 10 years  
Vesting schedule Vest 25% on the first anniversary date of the grant and remainder vest ratably over the following 36 months. Vest 25% on the first anniversary date of the grant and remainder vest ratably over the following 36 months. Vest 25% on the first anniversary date of the grant and remainder vest ratably over the following 36 months.  
Stock options [Member] | Incentive stock options granted to 10% ownership [Member] | Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Exercise price of stock options as percentage of fair market value at grant date 110.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amba_IncentiveStockOptionsTenPercentageOwnershipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		      
Stock options [Member] | Non statutory stock options and incentive stock options granted to less than 10% ownership [Member] | Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Exercise price of stock options as percentage of fair market value at grant date 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= amba_NonStatutoryStockOptionsAndIncentiveStockOptionsLessThanTenPercentageOwnershipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		      
Restricted stock units [Member] | 2012 Equity Incentive Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting schedule 1/4th of the shares on the first anniversary service date of the grant and 1/16th of the RSUs vest every 3 months thereafter, so as to be 100% vested on the fourth anniversary of the vesting commencement date. 1/4th of the shares on the first anniversary service date of the grant and 1/16th of the RSUs vest every 3 months thereafter, so as to be 100% vested on the fourth anniversary of the vesting commencement date. 1/4th of the shares on the first anniversary service date of the grant and 1/16th of the RSUs vest every 3 months thereafter, so as to be 100% vested on the fourth anniversary of the vesting commencement date.  
Restricted stock units [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Total unrecognized compensation cost, restricted stock units 48.7us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		      
Weighted average recognition period 2 years 10 months 24 days      
Aggregate intrinsic value of unvested restricted stock units 109.5us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember