| Document And Entity Information | Feb. 04, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | INPHI CORPORATION |
| Document, Type | 8-K |
| Document, Period End Date | Feb. 4, 2020 |
| Entity, File Number | 001-34942 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, Tax Identification Number | 77-0557980 |
| Entity, Address, Address Line One | 2953 Bunker Hill Lane |
| Entity, Address, Address Line Two | Suite 300 |
| Entity, Address, City or Town | Santa Clara |
| Entity, Address, State or Province | CA |
| Entity, Address, Postal Zip Code | 95054 |
| City Area Code | 408 |
| Local Phone Number | 217-7300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | IPHI |
| Security Exchange Name | NYSE |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001160958 |
