Subsequent Events - Additional Information (Detail) $ / shares in Units, shares in Thousands, $ in Millions			1 Months Ended						2 Months Ended	3 Months Ended					12 Months Ended			131 Months Ended	144 Months Ended
		Jul. 31, 2025 $ / shares shares	Nov. 30, 2025 $ / shares shares	[3]	Oct. 31, 2025 USD ($) $ / shares shares		Sep. 30, 2025 $ / shares shares	Aug. 31, 2025 $ / shares shares	Nov. 30, 2025 $ / shares shares	Sep. 30, 2025 $ / shares shares	Jun. 30, 2025 $ / shares shares	[1]	Mar. 31, 2025 $ / shares shares	Dec. 31, 2024 $ / shares shares	Sep. 30, 2025 USD ($) PartnershipUnit $ / shares shares	Sep. 30, 2024 USD ($) PartnershipUnit	Sep. 30, 2023 USD ($) PartnershipUnit	May 31, 2023 shares	Sep. 30, 2024 $ / shares shares
Heating Oil Businesses
Subsequent Event [Line Items]
Number of businesses acquired | PartnershipUnit															1	4	2
Aggregate purchase price partnership acquired															$ 80.5	$ 49.4	$ 19.8
Sale of certain assets															$ 0.3
Repurchase Plan
Subsequent Event [Line Items]
Company's common units repurchased and retired | shares		144					157	172		473	817		6	13	1,309			20,500	26,438
Average price paid per unit | $ / shares	[2]	$ 11.87					$ 11.73	$ 11.74		$ 11.78	$ 12.01		$ 11.24	$ 11.2	$ 11.92				$ 8.9
Subsequent Event | Repurchase Plan
Subsequent Event [Line Items]
Company's common units repurchased and retired | shares			67		234	[4]			300
Average price paid per unit | $ / shares			$ 11.83	[2]	$ 11.87	[2],[4]			$ 11.86
Subsequent Event | Dividend Declared
Subsequent Event [Line Items]
Distribution declared | $ / shares					0.185
Partners capital projected distribution amount on annualized basis | $ / shares					0.74
Minimum dividend distribution per unit | $ / shares					$ 0.0675
Amount to paid to common unit holders					$ 6.1
Amount to paid to the General Partner					0.4
Incentive distribution to the General Partner					0.4
Incentive distributions to management					$ 0.4
Dividend paid date					Nov. 05, 2025
Dividend record date					Oct. 27, 2025

[1] In May 2025, the Company purchased 700,000 Common Units in a private transaction for aggregate consideration of approximately $8.4 million. The purchase was made outside the Company’s unit repurchase plan.

[2] Amounts include repurchase costs.

[3] Of the total available for repurchase, approximately 0.5 million are available for repurchase in open market transactions and 0.1 million are available for repurchase in privately-negotiated transactions.

[4] In October 2025, the Company purchased 138,600 Common Units in a private transaction for aggregate consideration of approximately $1.6 million. The purchase was made within the Company’s unit repurchase plan.