| Document and Entity Information | Nov. 11, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001084048 |
| Document Type | 8-K |
| Document Period End Date | Nov. 11, 2019 |
| Entity Registrant Name | J2 Global, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 0-25965 |
| Entity Tax Identification Number | 47-1053457 |
| Entity Address, Address Line One | 6922 Hollywood Blvd. |
| Entity Address, Address Line Two | Suite 500 |
| Entity Address, City or Town | Los Angeles |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90028 |
| 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 |
| Security 12b Title | Common Stock, $0.01 par value |
| Trading Symbol | JCOM |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
