Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 28, 2025	Sep. 29, 2024	Dec. 31, 2024	Jul. 01, 2024	Oct. 31, 2020	Jun. 30, 2019	Apr. 30, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 5,050,740	$ 4,806,000	$ 4,960,000
Less current portion	(15,038)	(210,000)	(210,000)
Long term debt, gross, excluding current maturities	5,035,702	4,596,000	4,750,000
Less debt issuance costs and original issue discount	(45,351)	(44,494)	(49,562)
Plus acquisition fair value layers	21,582	23,001	22,634
Long-term debt	$ 5,011,933	$ 4,574,507	$ 4,723,072
2024 Credit Agreement \| Senior Secured Term Loan
Debt Instrument [Line Items]
Interest rate during period (as percent)	6.30%	7.30%	7.10%
Long-term debt, gross	$ 1,488,740	$ 1,000,000	$ 995,000
2027 senior unsecured notes at 5.375%
Debt Instrument [Line Items]
Interest rate (as percent)	5.375%
2027 senior unsecured notes at 5.375% \| Senior Unsecured Notes
Debt Instrument [Line Items]
Interest rate (as percent)	5.375%						5.375%
Long-term debt, gross	$ 500,000	500,000	500,000
2028 senior unsecured notes at 6.500%
Debt Instrument [Line Items]
Interest rate (as percent)	6.50%
2028 senior unsecured notes at 6.500% \| Senior Unsecured Notes
Debt Instrument [Line Items]
Interest rate (as percent)	6.50%				6.50%
Long-term debt, gross	$ 300,000	300,000	300,000
2029 senior unsecured notes at 5.250%
Debt Instrument [Line Items]
Interest rate (as percent)	5.25%
2029 senior unsecured notes at 5.250% \| Senior Unsecured Notes
Debt Instrument [Line Items]
Interest rate (as percent)	5.25%					5.25%
Long-term debt, gross	$ 500,000	500,000	500,000
2025 senior secured notes at 7.000%
Debt Instrument [Line Items]
Interest rate (as percent)	7.00%
2025 senior secured notes at 7.000% \| Secured Debt
Debt Instrument [Line Items]
Interest rate (as percent)	7.00%			7.00%
Long-term debt, gross	$ 0	200,000	200,000
2027 senior unsecured notes at 5.500%
Debt Instrument [Line Items]
Interest rate (as percent)	5.50%
2027 senior unsecured notes at 5.500% \| Senior Unsecured Notes
Debt Instrument [Line Items]
Interest rate (as percent)	5.50%			5.50%
Long-term debt, gross	$ 500,000	500,000	500,000
2031 senior unsecured notes at 7.250%
Debt Instrument [Line Items]
Interest rate (as percent)	7.25%
2031 senior unsecured notes at 7.250% \| Senior Unsecured Notes
Debt Instrument [Line Items]
Interest rate (as percent)	7.25%			7.25%
Long-term debt, gross	$ 800,000	800,000	800,000
2032 senior secured notes at 6.625%
Debt Instrument [Line Items]
Interest rate (as percent)	6.625%
2032 senior secured notes at 6.625% \| Secured Debt
Debt Instrument [Line Items]
Interest rate (as percent)	6.625%			6.625%
Long-term debt, gross	$ 850,000	$ 850,000	$ 850,000
Revolving Credit Facility \| Revolving credit facility averaging 6.4% YTD 2025, 7.4% in 2024 and 7.8% YTD 2024
Debt Instrument [Line Items]
Weighted average interest rate (as percent)	6.40%	7.80%	7.40%
Long-term debt, gross	$ 112,000	$ 156,000	$ 315,000

Six Flags Entertainment Corporation/NEW 10-Q