CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) shares in Thousands, $ in Thousands	Total	General Partner	Common Stock	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Sep. 30, 2022	$ 257,915	$ (3,656)	$ 277,177	$ (15,606)
Beginning Balance, unit at Sep. 30, 2022		326	36,092
Net income	31,945	$ 288	$ 31,657
Unrealized gain on pension plan obligation	1,463			1,463
Tax effect of unrealized gain on pension plan obligation	(405)			(405)
Unrealized gain (loss) on captive insurance collateral	1,671			1,671
Tax effect of unrealized gain (loss) on captive insurance collateral	(352)			(352)
Unrealized gain (loss) on interest rate hedge	(399)			(399)
Tax effect of unrealized gain (loss) on interest rate hedge	105			105
Distributions	(23,744)	(1,247)	(22,497)
Retirement of units	(4,475)		$ (4,475)
Retirement of units, shares			(489)
Ending Balance at Sep. 30, 2023	263,724	$ (4,615)	$ 281,862	(13,523)
Ending Balance, Unit at Sep. 30, 2023		326	35,603
Net income	35,223	$ 311	$ 34,912
Unrealized gain on pension plan obligation	1,291			1,291
Tax effect of unrealized gain on pension plan obligation	(262)			(262)
Unrealized gain (loss) on captive insurance collateral	1,849			1,849
Tax effect of unrealized gain (loss) on captive insurance collateral	(390)			(390)
Unrealized gain (loss) on interest rate hedge	(1,928)			(1,928)
Tax effect of unrealized gain (loss) on interest rate hedge	512			512
Distributions	(25,038)	(1,410)	(23,628)
Retirement of units	(11,088)		$ (11,088)
Retirement of units, shares			(1,016)
Ending Balance at Sep. 30, 2024	263,893	$ (5,714)	$ 282,058	(12,451)
Ending Balance, Unit at Sep. 30, 2024		326	34,587
Net income	73,495	$ 677	$ 72,818
Unrealized gain on pension plan obligation	1,468			1,468
Tax effect of unrealized gain on pension plan obligation	(388)			(388)
Unrealized gain (loss) on captive insurance collateral	328			328
Tax effect of unrealized gain (loss) on captive insurance collateral	(69)			(69)
Unrealized gain (loss) on interest rate hedge	(319)			(319)
Tax effect of unrealized gain (loss) on interest rate hedge	83			83
Distributions	(26,116)	(1,568)	(24,548)
Retirement of units	(15,595)		$ (15,595)
Retirement of units, shares			(1,309)
Ending Balance at Sep. 30, 2025	$ 296,780	$ (6,605)	$ 314,733	$ (11,348)
Ending Balance, Unit at Sep. 30, 2025		326	33,278