| Cover - USD ($) | 12 Months Ended | ||
| Dec. 31, 2019 | Feb. 29, 2020 | Jun. 30, 2019 | |
| Cover page. | |||
| Document Type | 10-K/A | ||
| Document Annual Report | true | ||
| Document Period End Date | Dec. 31, 2019 | ||
| Document Transition Report | false | ||
| Entity File Number | 1-38300 | ||
| Entity Registrant Name | CANNAE HOLDINGS, INC. | ||
| Entity Incorporation, State or 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 | ||
| Title of 12(b) Security | Cannae Common Stock, $0.0001 par value | ||
| Trading Symbol | CNNE | ||
| Security Exchange Name | NYSE | ||
| Entity Well-Known Seasoned Issuer | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Small Business | false | ||
| Entity Emerging Growth Company | false | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 1,941,307,497 | ||
| Entity Common Stock, Shares Outstanding | 79,516,833 | ||
| Amendment Flag | false | ||
| Document Fiscal Year Focus | 2019 | ||
| Document Fiscal Period Focus | FY | ||
| Entity Central Index Key | 0001704720 | ||
| Current Fiscal Year End Date | --12-31 |
