General - Basis of Presentation - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2022	Oct. 03, 2021	Oct. 02, 2022	Oct. 03, 2021
Calculation of earnings per share of common stock
Net income attributable to Six Flags Entertainment Corporation	$ 115,829	$ 157,241	$ 95,559	$ 131,922
Weighted-average common shares outstanding:
Weighted-average common shares outstanding - basic (in shares)	83,094,000	85,919,000	84,760,000	85,596,000
Effect of dilutive stock options and restricted stock units (in shares)	13,000	1,340,000	159,000	1,482,000
Weighted-average common shares outstanding-diluted (in shares)	83,107,000	87,259,000	84,919,000	87,078,000
Earnings (loss) per share - basic (in dollars per share)	$ 1.39	$ 1.83	$ 1.13	$ 1.54
Earnings (loss) per share - diluted (in dollars per share)	$ 1.39	$ 1.80	$ 1.13	$ 1.51
Antidilutive options
Antidilutive stock options excluded from computation of diluted shares outstanding (in shares)	2,509,000	3,580,000	2,979,000	3,528,000