Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Common stock	Capital in excess of par value	Accumulated deficit	Accumulated other comprehensive loss	Total
Beginning balance at Dec. 31, 2018	$ 2,099	$ 1,037,640	$ (1,611,334)	$ (71,498)	$ (643,093)
Beginning balance (in shares) at Dec. 31, 2018	83,962,182
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 8	12,391			12,399
Issuance of common stock (in shares)	345,479
Stock-based compensation		7,444			7,444
Dividends declared to common shareholders			(138,053)		(138,053)
Repurchase of common stock		(4)			(4)
Repurchase of common stock (in shares)	(67)
Employee stock purchase plan	$ 1	1,204			1,205
Employee stock purchase plan (in shares)	26,937
Fresh start valuation adjustment for partnership park units purchased			45		45
Net income (loss) attributable to Six Flags Entertainment Corporation			10,387		10,387
Net other comprehensive income (loss), net of tax				(137)	(137)
Ending balance at Jun. 30, 2019	$ 2,108	1,058,675	(1,738,955)	(71,635)	(749,807)
Ending balance (in shares) at Jun. 30, 2019	84,334,531
Beginning balance at Mar. 31, 2019	$ 2,106	1,052,378	(1,749,400)	(70,266)	(765,182)
Beginning balance (in shares) at Mar. 31, 2019	84,245,940
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 1	1,540			1,541
Issuance of common stock (in shares)	61,654
Stock-based compensation		3,553			3,553
Dividends declared to common shareholders			(69,119)		(69,119)
Employee stock purchase plan	$ 1	1,204			1,205
Employee stock purchase plan (in shares)	26,937
Fresh start valuation adjustment for partnership park units purchased			45		45
Net income (loss) attributable to Six Flags Entertainment Corporation			79,519		79,519
Net other comprehensive income (loss), net of tax				(1,369)	(1,369)
Ending balance at Jun. 30, 2019	$ 2,108	1,058,675	(1,738,955)	(71,635)	(749,807)
Ending balance (in shares) at Jun. 30, 2019	84,334,531
Beginning balance at Dec. 31, 2019	$ 2,116	1,066,223	(1,709,747)	(74,710)	(716,118)
Beginning balance (in shares) at Dec. 31, 2019	84,633,845
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 2	732			734
Issuance of common stock (in shares)	82,064
Stock-based compensation		10,300			10,300
Dividends declared to common shareholders			(21,165)		(21,165)
Repurchase of common stock		(6)			(6)
Repurchase of common stock (in shares)	(155)
Employee stock purchase plan	$ 1	717			718
Employee stock purchase plan (in shares)	41,532
Fresh start valuation adjustment for partnership park units purchased			924		924
Change in redemption value of partnership units		(18)			(18)
Net income (loss) attributable to Six Flags Entertainment Corporation			(221,440)		(221,440)
Net other comprehensive income (loss), net of tax				(24,711)	(24,711)
Ending balance at Jun. 30, 2020	$ 2,119	1,077,948	(1,951,428)	(99,421)	(970,782)
Ending balance (in shares) at Jun. 30, 2020	84,757,286
Beginning balance at Mar. 31, 2020	$ 2,116	1,070,900	(1,815,457)	(110,423)	(852,864)
Beginning balance (in shares) at Mar. 31, 2020	84,666,505
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 1	311			312
Issuance of common stock (in shares)	49,276
Stock-based compensation		6,020			6,020
Dividends declared to common shareholders			(1)		(1)
Employee stock purchase plan	$ 2	717			719
Employee stock purchase plan (in shares)	41,505
Fresh start valuation adjustment for partnership park units purchased			924		924
Net income (loss) attributable to Six Flags Entertainment Corporation			(136,894)		(136,894)
Net other comprehensive income (loss), net of tax				11,002	11,002
Ending balance at Jun. 30, 2020	$ 2,119	$ 1,077,948	$ (1,951,428)	$ (99,421)	$ (970,782)
Ending balance (in shares) at Jun. 30, 2020	84,757,286