| Document and Entity Information | Dec. 20, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | VIASAT INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000797721 |
| Document Type | 8-K |
| Document Period End Date | Dec. 20, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 000-21767 |
| Entity Tax Identification Number | 33-0174996 |
| Entity Address, Address Line One | 6155 El Camino Real |
| Entity Address, City or Town | Carlsbad |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92009 |
| City Area Code | (760) |
| Local Phone Number | 476-2200 |
| Written Communications | true |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.0001 per share |
| Trading Symbol | VSAT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
