Long-Term Debt and Bank Facility Borrowings - Additional Information (Detail) - USD ($)				3 Months Ended
		Jan. 25, 2022	Dec. 04, 2019	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Debt Instrument [Line Items]
Additional term loan repayments				$ 7,871,000	$ 3,250,000
Hedging positions and payable amounts secured under credit facility				0		$ 0
Letters of credit issued and outstanding				5,100,000		3,100,000
Long-term debt, fair value	[1]			226,311,000		119,118,000
Revolving credit facility outstanding				123,682,000		8,618,000
Availability under credit agreement				$ 136,600,000		$ 171,500,000
Term Loan
Debt Instrument [Line Items]
Debt instrument, effective interest rate				4.30%		4.30%
Long-term debt, fair value	[1],[2]			$ 102,629,000		$ 110,500,000
Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, effective interest rate				2.70%		2.50%
Revolving credit facility outstanding				$ 123,700,000		$ 8,600,000
Credit Agreement
Debt Instrument [Line Items]
Non Seasonal maximum borrowing capacity under revolving credit facility			$ 300,000,000
Maximum borrowing capacity (heating season December to April) under revolving credit facility			450,000,000
Issuance of line of credit for working capital purposes			$ 25,000,000
Senior secured term loan maturity date			Dec. 04, 2024
Facility size that can be increased without consulting bank group			$ 200,000,000
Term loan annual payment percentage			25.00%
Additional term loan repayments				$ 4,600,000
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%
Availability percentage to maximum facility size			12.50%
Credit Agreement | Maximum
Debt Instrument [Line Items]
Senior secured leverage ratio during quarters ending June or September			300.00%
Senior secured leverage ratio during quarters ending December or March			450.00%
Credit Agreement | Quarterly
Debt Instrument [Line Items]
Term loan periodic payment			$ 3,250,000
Credit Agreement | Annually | Maximum
Debt Instrument [Line Items]
Term loan periodic payment			12,000,000
Credit Agreement | Term Loan
Debt Instrument [Line Items]
Outstanding term loan			$ 130,000,000
Senior secured term loan maturity period			5 years
Credit Agreement | Subsequent Event
Debt Instrument [Line Items]
Non Seasonal maximum borrowing capacity under revolving credit facility		$ 350,000,000
Increase in revolving credit facility		$ 50,000,000

[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 $0.4 million as of December 31, 2021 and $0.5 million as of September 30, 2021.