| Document and Entity Information | Nov. 18, 2019 |
| Cover [Abstract] | |
| Entity Registrant Name | 8X8 INC /DE/ |
| Amendment Flag | false |
| Entity Central Index Key | 0001023731 |
| Document Type | 8-K |
| Document Period End Date | Nov. 18, 2019 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38312 |
| Entity Tax Identification Number | 77-0142404 |
| Entity Address, Address Line One | 2125 O’Nel Drive |
| Entity Address, City or Town | San Jose |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95131 |
| City Area Code | (408) |
| Local Phone Number | 727-1885 |
| Security 12b Title | Common Stock, $.001 par value |
| Trading Symbol | EGHT |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
