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		96 Months Ended	97 Months Ended
		Oct. 01, 2021 USD ($) PartnershipUnit	Nov. 30, 2021 $ / shares shares		Oct. 31, 2021 USD ($) $ / shares shares		Sep. 30, 2021 USD ($) $ / shares shares	Aug. 31, 2021 $ / shares shares	Jul. 31, 2021 $ / shares shares	Nov. 30, 2021 $ / shares shares	Sep. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2021 $ / shares shares	Mar. 31, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares	Sep. 30, 2021 USD ($) PartnershipUnit $ / shares shares	Sep. 30, 2020 USD ($) PartnershipUnit	Sep. 30, 2020 USD ($) $ / shares shares	Jul. 31, 2020 shares
Heating Oil Dealers
Subsequent Event [Line Items]
Aggregate purchase price partnership acquired															$ 42.5	$ 3.3
Number of businesses acquired | PartnershipUnit															3	2
Aggregate purchase price allocation, goodwill and intangible assets							$ 37.3				$ 37.3				$ 37.3	$ 3.2	$ 3.2
Aggregate purchase price allocation, fixed assets							6.2				6.2				6.2	0.6	0.6
Gross purchase price increased (reduced) by working capital credits							$ (1.0)				$ (1.0)				$ (1.0)	$ 0.5	$ 0.5
Repurchase Plan
Subsequent Event [Line Items]
Company's common units repurchased and retired | shares							337	223	25		585	568	538	2,591	4,282		17,697	14,400
Average price paid per unit | $ / shares	[1]						$ 10.30	$ 10.68	$ 11.27		$ 10.49	$ 10.94	$ 9.67	$ 9.75	$ 10.00		$ 8.26
Subsequent Event | Heating Oil Dealers
Subsequent Event [Line Items]
Aggregate purchase price partnership acquired		$ 3.3
Number of businesses acquired | PartnershipUnit		3
Aggregate purchase price allocation, goodwill and intangible assets		$ 2.9
Aggregate purchase price allocation, fixed assets		1.2
Gross purchase price increased (reduced) by working capital credits		$ (0.8)
Subsequent Event | Repurchase Plan
Subsequent Event [Line Items]
Company's common units repurchased and retired | shares			161		273					400
Average price paid per unit | $ / shares			$ 10.99	[1]	$ 10.67	[1]				$ 10.79
Subsequent Event | Dividend Declared
Subsequent Event [Line Items]
Distribution declared | $ / shares					0.1425
Partners capital projected distribution amount on annualized basis | $ / shares					0.57
Minimum dividend distribution per unit | $ / shares					$ 0.0675
Amount to paid to common unit holders					$ 5.5
Amount to paid to the General Partner					0.3
Incentive distribution to the General Partner					0.2
Incentive distributions to management					$ 0.2
Dividend paid date					Nov. 09, 2021
Dividend record date					Nov. 01, 2021

[1] Amounts include repurchase costs.