Condensed Financial Information of Registrant Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Cash flows provided by operating activities:
Net cash provided by operating activities	$ 33,907	$ 68,877	$ 175,668
Cash flows provided by investing activities:
Net cash provided by investing activities	(32,626)	(50,326)	(28,141)
Cash flows used in financing activities:
Distributions	(23,192)	(23,448)	(24,451)
Unit repurchase	(30,817)	(42,824)	(38,431)
Net cash provided by (used in) financing activities	8,572	(70,695)	(95,515)
Net decrease in cash	9,853	(52,144)	52,012
Cash and cash equivalents at beginning of period	4,767
Cash and cash equivalents at end of period	14,620	4,767
STAR GROUP, L.P.
Cash flows provided by operating activities:
Net cash provided by operating activities	54,005	66,272	62,877
Cash flows provided by investing activities:
Net cash provided by investing activities	0	0	0
Cash flows used in financing activities:
Distributions	(23,192)	(23,448)	(24,451)
Unit repurchase	(30,817)	(42,824)	(38,431)
Net cash provided by (used in) financing activities	(54,009)	(66,272)	(62,882)
Net decrease in cash	(4)	(0)	(5)
Cash and cash equivalents at beginning of period	45	45	50
Cash and cash equivalents at end of period	$ 41	$ 45	$ 45