| Document and Entity Information | Jun. 11, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 11, 2021 |
| Entity File Number | 001-37394 |
| Entity Registrant Name | BLACK KNIGHT, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 81-5265638 |
| Entity Address, Address Line One | 601 Riverside Avenue |
| Entity Address, City or Town | Jacksonville |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 32204 |
| City Area Code | 904 |
| Local Phone Number | 854-5100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value |
| Trading Symbol | BKI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001627014 |
| Amendment Flag | false |
