Consolidated Statements of Equity (Deficit) - USD ($) $ in Thousands	Common stock	Capital in excess of par value	Accumulated deficit	Accumulated other comprehensive loss	Total
Increase (Decrease) in Stockholders' Deficit
Cumulative effect adjustment | Accounting Standards Update 2016-09			$ 98,657		$ 98,657
Adjusted balance	$ 2,271	$ 1,116,227	(1,139,147)	$ (67,184)	(87,833)
Beginning balance at Dec. 31, 2016	$ 2,271	1,116,227	(1,237,804)	(67,184)	(186,490)
Beginning balance (in shares) at Dec. 31, 2016	90,849,428
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 50	60,533			60,583
Issuance of common stock (in shares)	1,980,939
Stock-based compensation		(22,697)			(22,697)
Dividends declared to common shareholders			(226,078)		(226,078)
Repurchase of common stock	$ (210)	(61,001)	(438,231)		(499,442)
Repurchase of common stock (in shares)	(8,377,729)
Employee stock purchase plan	$ 1	1,918			1,919
Employee stock purchase plan (in shares)	35,795
Fresh start valuation adjustment for SFOT units purchased			32		32
Change in redemption value of partnership units		(8,715)			(8,715)
Net income attributable to Six Flags Entertainment Corporation			273,816		273,816
Other comprehensive income (loss), net of tax				3,303	3,303
Ending balance at Dec. 31, 2017	$ 2,112	1,086,265	(1,529,608)	(63,881)	(505,112)
Ending balance (in shares) at Dec. 31, 2017	84,488,433
Increase (Decrease) in Stockholders' Deficit
Cumulative effect adjustment | Accounting Standards Update 2014-09 and 2018-02			4,557	(9,439)	(4,882)
Adjusted balance	$ 2,112	1,086,265	(1,525,051)	(73,320)	(509,994)
Issuance of common stock	$ 31	41,626			41,657
Issuance of common stock (in shares)	1,264,497
Stock-based compensation		(46,684)			(46,684)
Dividends declared to common shareholders			(265,755)		(265,755)
Repurchase of common stock	$ (45)	(14,341)	(96,604)		(110,990)
Repurchase of common stock (in shares)	(1,827,991)
Employee stock purchase plan	$ 1	2,047			2,048
Employee stock purchase plan (in shares)	37,243
Fresh start valuation adjustment for SFOT units purchased			80		80
Change in redemption value of partnership units		(31,273)			(31,273)
Change in redemption value of partnership units					(31,273)
Net income attributable to Six Flags Entertainment Corporation			275,996		275,996
Other comprehensive income (loss), net of tax				1,822	1,822
Ending balance at Dec. 31, 2018	$ 2,099	1,037,640	(1,611,334)	(71,498)	(643,093)
Ending balance (in shares) at Dec. 31, 2018	83,962,182
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 16	17,480			17,496
Issuance of common stock (in shares)	622,787
Stock-based compensation		13,274			13,274
Dividends declared to common shareholders			(277,523)		(277,523)
Repurchase of common stock		(52)			(52)
Repurchase of common stock (in shares)	(882)
Employee stock purchase plan	$ 1	2,130			2,131
Employee stock purchase plan (in shares)	49,758
Fresh start valuation adjustment for SFOT units purchased			45		45
Change in redemption value of partnership units		(4,249)			(4,249)
Change in redemption value of partnership units					(4,249)
Net income attributable to Six Flags Entertainment Corporation			179,065		179,065
Other comprehensive income (loss), net of tax				(3,212)	(3,212)
Ending balance at Dec. 31, 2019	$ 2,116	$ 1,066,223	$ (1,709,747)	$ (74,710)	$ (716,118)
Ending balance (in shares) at Dec. 31, 2019	84,633,845