| Document and Entity Information | Feb. 23, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001463172 |
| Document Type | 8-K |
| Document Period End Date | Feb. 23, 2021 |
| Entity Registrant Name | ZENDESK, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36456 |
| Entity Tax Identification Number | 26-4411091 |
| Entity Address, Address Line One | 989 Market Street |
| Entity Address, City or Town | San Francisco |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94103 |
| City Area Code | (415) |
| Local Phone Number | 418-7506 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | ZEN |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
