| Document and Entity Information | Jan. 25, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001704720 |
| Document Type | 8-K |
| Document Period End Date | Jan. 25, 2021 |
| Entity Registrant Name | CANNAE HOLDINGS, INC. |
| Entity File Number | 1-38300 |
| Entity Incorporation State Country Code | DE |
| Entity Tax Identification Number | 82-1273460 |
| Entity Address, Address Line One | 1701 Village Center Circle |
| Entity Address, City or Town | Las Vegas |
| Entity Address, State or Province | NV |
| Entity Address, Postal Zip Code | 89134 |
| City Area Code | (702) |
| Local Phone Number | 323-7330 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Cannae Common Stock, $0.0001 par value |
| Trading Symbol | CNNE |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
