| Document and Entity Information | Feb. 24, 2021 |
| Document and Entity Information | |
| Document Type | 8-K |
| Document Period End Date | Feb. 24, 2021 |
| Entity Registrant Name | Six Flags Entertainment Corporation |
| Entity File Number | 1-13703 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 13-3995059 |
| Entity Address, Address Line One | 1000 Ballpark Way Suite 400 |
| Entity Address, City or Town | Arlington |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 76011 |
| City Area Code | 972 |
| Local Phone Number | 595-5000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000701374 |
| Amendment Flag | false |
| Common Stock | |
| Document and Entity Information | |
| Title of 12(b) Security | Common stock, $0.025 par value per share |
| Trading Symbol | SIX |
| Security Exchange Name | NYSE |
| Preferred Stock | |
| Document and Entity Information | |
| Title of 12(b) Security | Preferred Stock Purchase Rights |
| Trading Symbol | SIX |
| Security Exchange Name | NYSE |
