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Segment Reporting - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Apr. 30, 2015
Segment
Apr. 30, 2014
Jan. 31, 2015
Concentration Risk [Line Items]      
Number of reportable segment 1us-gaap_NumberOfReportableSegments    
Long-lived assets $ 3,022us-gaap_PropertyPlantAndEquipmentNet   $ 3,075us-gaap_PropertyPlantAndEquipmentNet
Accounts receivable 39,193us-gaap_AccountsReceivableNetCurrent   40,180us-gaap_AccountsReceivableNetCurrent
Wintech And Chicony [Member]      
Concentration Risk [Line Items]      
Accounts receivable 36,100us-gaap_AccountsReceivableNetCurrent
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
  36,200us-gaap_AccountsReceivableNetCurrent
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
Wintech And Chicony [Member] | Sales revenue, net [Member] | Customer concentration risk [Member]      
Concentration Risk [Line Items]      
Percentage of revenue 91.00%amba_MajorCustomerRevenuePercentage
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
86.00%amba_MajorCustomerRevenuePercentage
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
 
Wintech And Chicony [Member] | Sales revenue, net [Member] | Customer concentration risk [Member] | Minimum [Member]      
Concentration Risk [Line Items]      
Percentage of revenue or accounts receivable 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Wintech And Chicony [Member] | Accounts receivable [Member] | Credit concentration risk [Member] | Minimum [Member]      
Concentration Risk [Line Items]      
Percentage of revenue or accounts receivable 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amba_WintechAndChiconyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
United States [Member]      
Concentration Risk [Line Items]      
Long-lived assets 1,900us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_StatementGeographicalAxis
= country_US
   
Asia Pacific [Member]      
Concentration Risk [Line Items]      
Long-lived assets $ 1,100us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_StatementGeographicalAxis
= us-gaap_AsiaPacificMember