| Cover | Aug. 20, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 20, 2021 |
| Entity Registrant Name | SERVICENOW, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-35580 |
| Entity Tax Identification Number | 20-2056195 |
| Entity Address, Address Line One | 2225 Lawson Lane |
| Entity Address, City or Town | Santa Clara |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95054 |
| City Area Code | 408 |
| Local Phone Number | 501-8550 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.001 per share |
| Trading Symbol | NOW |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001373715 |
| Amendment Flag | false |
