Long-Term Debt and Bank Facility Borrowings - Additional Information (Detail) - USD ($)			12 Months Ended
		Sep. 27, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Additional loan repayments			$ 148,500,000	$ 16,500,000	$ 110,500,000
Hedging positions and payable amounts secured under credit facility			14,200,000	100,000
Letters of credit issued and outstanding			5,200,000	3,200,000
Long-term debt, fair value	[1]		210,005,000	148,740,000
Revolving credit facility outstanding			5,000	240,000
Availability under credit agreement			166,500,000	202,100,000
Total restricted net assets			254,000,000	$ 253,700,000
Credit Agreement
Debt Instrument [Line Items]
Non Seasonal maximum borrowing capacity under revolving credit facility		$ 400,000,000
Maximum borrowing capacity (heating season December to April) under revolving credit facility		475,000,000
Issuance of line of credit for working capital purposes		$ 25,000,000
Senior secured term loan maturity date		Sep. 27, 2029
Facility size that can be increased without consulting bank group		$ 200,000,000
Term loan annual payment percentage		25.00%
Commitment fee on the unused portion of the facility from December through April		0.30%
Commitment fee on the unused portion of the facility from May through November		0.20%
Minimum fixed charge coverage ratio		110.00%
Facility size that can be increased additional without consulting bank group			200,000,000
Maximum | Credit Agreement
Debt Instrument [Line Items]
Availability percentage to maximum facility size		12.50%
Senior secured leverage ratio during quarters ending June or September		300.00%
Senior secured leverage ratio during quarters ending December or March		550.00%
Maximum facility size		$ 35,000,000
Quarterly | Credit Agreement
Debt Instrument [Line Items]
Term loan periodic payment		5,300,000
Annually | Maximum | Credit Agreement
Debt Instrument [Line Items]
Term loan periodic payment		4,000,000
Term Loan
Debt Instrument [Line Items]
Additional loan repayments			$ 4,000,000
Debt instrument, effective interest rate			7.20%	6.60%
Long-term debt, fair value	[1],[2]		$ 210,000,000	$ 148,500,000
Term Loan | Credit Agreement
Debt Instrument [Line Items]
Outstanding term loan		$ 210,000,000
Senior secured term loan maturity period		5 years
Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, effective interest rate			7.50%	6.30%
Revolving credit facility outstanding				$ 200,000
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Revolving credit facility outstanding			$ 100,000

[1] The face amount of the Company’s variable rate long-term debt approximates fair value.

[2] Carrying amounts are net of unamortized debt issuance costs of $1.2 million as of September 30, 2024 and $0.7 million as of September 30, 2023.