General - Basis of Presentation - Earnings (loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2022	Jul. 04, 2021	Jul. 03, 2022	Jul. 04, 2021
Calculation of earnings per share of common stock
Net income (loss) attributable to Six Flags Entertainment Corporation	$ 45,392	$ 70,520	$ (20,270)	$ (25,319)
Weighted-average common shares outstanding:
Weighted-average common shares outstanding - basic (in shares)	84,992,000	85,673,000	85,594,000	85,437,000
Effect of dilutive stock options and restricted stock units (in shares)	250,000	1,078,000
Weighted-average common shares outstanding-diluted (in shares)	85,242,000	86,751,000	85,594,000	85,437,000
Earnings (loss) per share - basic (in dollars per share)	$ 0.53	$ 0.82	$ (0.24)	$ (0.30)
Earnings (loss) per share - diluted (in dollars per share)	$ 0.53	$ 0.81	$ (0.24)	$ (0.30)
Antidilutive options
Antidilutive stock options excluded from computation of diluted shares outstanding (in shares)	2,462,000	3,509,000	2,415,000	5,247,000