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Subsequent Events - Additional Information (Detail) - USD ($)	Jun. 04, 2018	May 31, 2017
Subsequent Event [Line Items]
Stock repurchase program, period		12 months
Stock repurchase program, commencing date		Jul. 01, 2017
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock repurchase program, period	12 months
Stock repurchase program, commencing date	Jun. 05, 2018
Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Amount authorized under stock repurchase program	$ 100,000,000

X

- Definition

Stock repurchase program commencement date.

+ References

No definition available.

+ Details

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Namespace Prefix:	amba_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Period which shares may be purchased under a stock repurchase plan authorized by an entity's Board of Directors, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: