Long-Term Debt and Bank Facility Borrowings - Additional Information (Detail) - USD ($)			9 Months Ended		12 Months Ended
		Jul. 06, 2022	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Term loan periodic payment			$ 8,500,000
Additional term loan repayments			14,615,000	$ 9,750,000
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]		225,395,000			119,118,000
Revolving credit facility outstanding			60,395,000			8,618,000
Availability under credit agreement			124,400,000			$ 171,500,000
Term Loan
Debt Instrument [Line Items]
Additional term loan repayments			$ 95,900,000
Debt instrument, effective interest rate			4.40%			4.30%
Long-term debt, fair value	[1],[2]		$ 95,885,000			$ 110,500,000
Revolving Credit Facility
Debt Instrument [Line Items]
Additional term loan repayments			$ 69,100,000
Debt instrument, effective interest rate			2.30%			2.50%
Revolving credit facility outstanding			$ 129,500,000			$ 8,600,000
Credit Agreement
Debt Instrument [Line Items]
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
Credit Agreement | Scenario Forecast
Debt Instrument [Line Items]
Additional term loan repayments					$ 4,900,000
Subsequent Event
Debt Instrument [Line Items]
Extended maturity date		Jul. 06, 2027
Subsequent Event | 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		550,000
Issuance of line of credit for working capital purposes		$ 25,000,000
Senior secured term loan maturity date		Jul. 06, 2027
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%
Availability percentage to maximum facility size		12.50%
Subsequent Event | 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		5.50%
Subsequent Event | Credit Agreement | Quarterly
Debt Instrument [Line Items]
Term loan periodic payment		$ 4,100,000
Subsequent Event | Credit Agreement | Term Loan
Debt Instrument [Line Items]
Outstanding term loan		$ 165,000,000
Senior secured term loan maturity period		5 years
Increase in term loan		$ 165,000,000
Additional term loan repayments		95,900,000
Subsequent Event | Credit Agreement | Revolving Credit Facility
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		550,000,000
Additional term loan repayments		$ 69,100,000

[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 $0.4 million as of June 30, 2022 and $0.5 million as of September 30, 2021