| Cover | Nov. 10, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 10, 2020 |
| Entity Registrant Name | PERSPECTA INC. |
| Entity Incorporation, State or Country Code | NV |
| Entity File Number | 001-38395 |
| Entity Tax Identification Number | 82-3141520 |
| Entity Address, Address Line One | 14295 Park Meadow Drive |
| Entity Address, City or Town | Chantilly |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 20151 |
| City Area Code | 571 |
| Local Phone Number | 313-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value per share |
| Trading Symbol | PRSP |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001724670 |
