| Document and Entity Information Document | Dec. 22, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 22, 2020 |
| Entity Registrant Name | J2 Global, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 0-25965 |
| Entity Tax Identification Number | 47-1053457 |
| Entity Address, Address Line One | 700 S. Flower Street, |
| Entity Address, Address Line Two | 15th Floor |
| Entity Address, City or Town | Los Angeles |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90017 |
| City Area Code | 323 |
| Local Phone Number | 860-9200 |
| 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 |
| Trading Symbol | JCOM |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001084048 |
| Amendment Flag | false |
