| Document and Entity Information | Mar. 11, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001551693 |
| Document Type | 8-K |
| Document Period End Date | Mar. 11, 2021 |
| Entity Registrant Name | SIENTRA, INC. |
| Entity File Number | 001-36709 |
| Entity Incorporation State Country Code | DE |
| Entity Tax Identification Number | 20-5551000 |
| Entity Address, Address Line One | 420 South Fairview Avenue |
| Entity Address, Address Line Two | Suite 200 |
| Entity Address, City or Town | Santa Barbara |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 93117 |
| City Area Code | (805) |
| Local Phone Number | 562-3500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Security12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | SIEN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
