Long-Term Debt and Bank Facility Borrowings - Additional Information (Detail) - USD ($)			3 Months Ended	9 Months Ended
		Sep. 27, 2024	Dec. 31, 2023	Jun. 30, 2025	Jun. 30, 2024	Sep. 30, 2024
Debt Instrument [Line Items]
Additional loan repayments				$ 15,750,000	$ 12,250,000
Hedging positions and payable amounts secured under credit facility				2,200,000		$ 14,200,000
Letters of credit issued and outstanding				5,200,000		5,200,000
Long-term debt, fair value	[1]			194,250,000		210,005,000
Revolving credit facility outstanding				0		5,000
Availability under credit agreement				$ 167,600,000		$ 166,500,000
Term Loan
Debt Instrument [Line Items]
Term loan annual payment percentage			25.00%
Additional loan repayments			$ 4,000,000.0
Debt instrument, effective interest rate				7.10%		7.20%
Long-term debt, fair value	[1],[2]			$ 194,250,000		$ 210,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, effective interest rate				6.40%		7.50%
Revolving credit facility outstanding				$ 0
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 additional without consulting bank group				200,000,000
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%
Credit Agreement | Quarterly
Debt Instrument [Line Items]
Term loan periodic payment		$ 5,300,000
Credit Agreement | Term Loan
Debt Instrument [Line Items]
Outstanding term loan		$ 210,000,000
Senior secured term loan maturity period		5 years
Maximum | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility outstanding						$ 100,000
Maximum | Credit Agreement
Debt Instrument [Line Items]
Availability percentage to maximum facility size		12.50%
Maximum facility size		$ 35,000,000
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 | Credit Agreement | Annually
Debt Instrument [Line Items]
Term loan periodic payment		$ 4,000,000

[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 $1.0 million as of June 30, 2025 and $1.2 million as of September 30, 2024