Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information (Unaudited)
Revenues	$ 261,000	$ 621,180	$ 477,210	$ 128,193	$ 269,503	$ 619,820	$ 445,420	$ 128,964			$ 1,487,583	$ 1,463,707	$ 1,359,074
Income before income taxes	10,143	261,835	133,571	(93,789)	115,781	259,681	118,418	(82,020)			311,760	411,858	329,052
Net (loss) income attributable to Six Flags Entertainment Corporation common stockholders	$ (11,155)	$ 179,833	$ 79,519	$ (69,132)	$ 79,422	$ 184,417	$ 74,502	$ (62,345)			$ 179,065	$ 275,996	$ 273,816
Net (loss) income per weighted average common share outstanding:
Earnings per share - basic (in dollars per share)	$ (0.13)	$ 2.13	$ 0.94	$ (0.82)	$ 0.94	$ 2.19	$ 0.89	$ (0.74)			$ 2.12	$ 3.28	$ 3.15
Earnings per share - diluted (in dollars per share)	$ (0.13)	$ 2.11	$ 0.94	$ (0.82)	$ 0.93	$ 2.16	$ 0.88	$ (0.74)			$ 2.11	$ 3.23	$ 3.09
2017 Performance Award | Long Term Incentive Plan
Stock Benefit Plans
Cumulative adjustment to allocated share-based compensation expense					$ 81,700				$ 45,000	$ 27,900