Condensed Financial Information of Registrant Balance Sheets (Detail) - USD ($) $ in Thousands		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Current assets
Cash and cash equivalents		$ 14,620	$ 4,767
Prepaid expenses and other current assets		32,016	30,140
Total current assets		288,263	221,992
Total assets		912,475	853,863
Current liabilities
Accrued expenses		125,561	121,221
Total current liabilities		381,080	344,997
Partners’ capital		257,915	278,204	$ 255,820	$ 260,840
Total liabilities and partners’ capital		912,475	853,863
STAR GROUP, L.P.
Current assets
Cash and cash equivalents		41	45	$ 45	$ 50
Prepaid expenses and other current assets		376	353
Total current assets		417	398
Investment in subsidiaries	[1]	257,554	277,817
Total assets		257,971	278,215
Current liabilities
Accrued expenses		56	11
Total current liabilities		56	11
Partners’ capital		257,915	278,204
Total liabilities and partners’ capital		$ 257,971	$ 278,215

[1] Investments in Star Acquisitions, Inc. and subsidiaries are recorded in accordance with the equity method of accounting.