| Document and Entity Information | Mar. 11, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | SYNAPTICS Inc |
| Amendment Flag | false |
| Entity Central Index Key | 0000817720 |
| Document Type | 8-K |
| Document Period End Date | Mar. 11, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 000-49602 |
| Entity Tax Identification Number | 77-0118518 |
| Entity Address, Address Line One | 1251 McKay 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 | 904-1100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $.001 per share |
| Trading Symbol | SYNA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
