| Cover Cover | Nov. 12, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 12, 2020 |
| Entity Registrant Name | Alpha and Omega Semiconductor Limited |
| Entity Incorporation, State or Country Code | D0 |
| Entity File Number | 001-34717 |
| Entity Tax Identification Number | 77-0553536 |
| Entity Address, Address Line One | Clarendon House |
| Entity Address, Address Line Two | 2 Church Street |
| Entity Address, City or Town | Hamilton |
| Entity Address, Postal Zip Code | HM 11 |
| Entity Address, Country | BM |
| City Area Code | 408 |
| Local Phone Number | 830-9742 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Shares |
| Trading Symbol | AOSL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001387467 |
| Amendment Flag | false |
