Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance (Detail)	Apr. 30, 2013	Jan. 31, 2013
Equity [Abstract]
Shares reserved for options and restricted stock units	6,836,469	5,818,126
Shares reserved for employee stock purchase plan	798,383	460,445
Shares reserved for warrants	11,167	36,292

Ordinary shares reserved for future issuance of stock options and restricted stock units.

No definition available.

Name:	amba_OrdinarySharesReservedForFutureIssuanceOfStockOptionAndRestrictedStockUnits
Namespace Prefix:	amba_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant