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Long-Term Indebtedness - Additional Information (Details) $ in Thousands							1 Months Ended	9 Months Ended
	Apr. 22, 2020 USD ($)	Oct. 18, 2019 USD ($)	Oct. 17, 2019	Apr. 17, 2019 USD ($)	Apr. 13, 2017 USD ($)	Jun. 16, 2016 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Apr. 30, 2020 USD ($)	Apr. 08, 2020 USD ($)	Apr. 07, 2020 USD ($)	Dec. 31, 2019 USD ($)	Aug. 31, 2019 USD ($)	Apr. 16, 2019 USD ($)
Summary of Long-term debt
Payments of debt issuance costs								$ 22,271	$ 8,927
Loss on debt extinguishment, net								6,106	$ 6,231
Proceeds from issuance of debt utilized for extinguishment of existing debt instruments						$ 150,000
Amended And Restated Revolving Loan
Summary of Long-term debt
Maximum borrowing capacity								481,000
Amended and Restated Term Loan B
Summary of Long-term debt
Maximum borrowing capacity								479,000
Loss on debt extinguishment, net	$ 5,100
Repayment of debt	315,000
2015 Revolving Loan
Summary of Long-term debt
Maximum borrowing capacity															$ 250,000
Credit Facility 2015 - Term Loan B
Summary of Long-term debt
Maximum borrowing capacity															$ 700,000
Second Amended and Restated Credit Facility
Summary of Long-term debt
Payments of debt issuance costs				$ 8,900
Second Amended and Restated Revolving Loan
Summary of Long-term debt
Maximum borrowing capacity				350,000							$ 481,000	$ 350,000
Long-term line of credit								0					$ 0
Letters of credit outstanding, amount								$ 21,700					20,800
Commitment fee percentage								0.625%
Incremental borrowing capacity								$ 131,000			$ 131,000
Second Amended and Restated Term Loan B
Summary of Long-term debt
Maximum borrowing capacity				800,000			$ 350,000			$ 481,000
Basis spread reduction		25.00%
Loss on debt extinguishment, net		$ 2,000		$ 6,200
Long-term line of credit													796,000
Incremental borrowing capacity										131,000
Long-term debt								$ 479,000					796,000
Interest rate, stated percentage								3.01%
Repayment of debt	315,000
Annual interest cost savings from borrowing rate reduction		$ 300
Second Amended and Restated Term Loan B \| Interest Rate Swap Second Agreements
Summary of Long-term debt
Number of agreements														2
Notional amount														$ 400,000
Second Amended and Restated Term Loan B \| LIBOR
Summary of Long-term debt
Basis spread on variable rate		1.75%	2.00%					1.75%
Senior Unsecured 2024 Notes
Summary of Long-term debt
Loss on debt extinguishment, net							1,000
Long-term debt							949,500	$ 949,490					1,000,000
Debt instrument, face amount						$ 300,000
Interest rate, stated percentage						4.875%
Periodic payment of interest							23,100
Pre-payment							$ 50,500
Senior Unsecured 2024 Notes Add-on
Summary of Long-term debt
Debt instrument, face amount					$ 700,000
Interest rate, stated percentage					4.875%
Senior Unsecured 2025 Notes
Summary of Long-term debt
Long-term debt								725,000
Debt instrument, face amount										$ 725,000
Interest rate, stated percentage										7.00%
Periodic payment of interest								25,400
Period payment of interest - first payment								35,100
Senior Unsecured 2025 Notes \| Six Flags Theme Parks Inc.
Summary of Long-term debt
Debt instrument, face amount	$ 725,000
Interest rate, stated percentage	7.00%
Senior Unsecured 2027 Notes
Summary of Long-term debt
Long-term debt								$ 500,000					$ 500,000
Debt instrument, face amount					$ 500,000
Interest rate, stated percentage					5.50%
Periodic payment of interest					$ 13,800