CONDENSED CONSOLIDATED STATEMENT 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 (loss)	51,674	$ 468	$ 51,206
Unrealized gain on pension plan obligation	1,144			1,144
Tax effect of unrealized gain on pension plan obligation	(305)			(305)
Unrealized gain (loss) on captive insurance collateral	1,080			1,080
Tax effect of unrealized gain (loss) on captive insurance collateral	(227)			(227)
Unrealized gain (loss) on interest rate hedges	(510)			(510)
Tax effect of unrealized gain (loss) on interest rate hedges	137			137
Distributions	(17,624)	(915)	(16,709)
Retirement of units	(4,475)		$ (4,475)
Retirement of units, shares			(489)
Ending Balance at Jun. 30, 2023	288,809	$ (4,103)	$ 307,199	(14,287)
Ending Balance, Unit at Jun. 30, 2023		326	35,603
Beginning Balance at Mar. 31, 2023	318,175	$ (3,553)	$ 336,674	(14,946)
Beginning Balance, unit at Mar. 31, 2023		326	35,603
Net income (loss)	(23,906)	$ (216)	$ (23,690)
Unrealized gain on pension plan obligation	382			382
Tax effect of unrealized gain on pension plan obligation	(104)			(104)
Unrealized gain (loss) on captive insurance collateral	(50)			(50)
Tax effect of unrealized gain (loss) on captive insurance collateral	11			11
Unrealized gain (loss) on interest rate hedges	571			571
Tax effect of unrealized gain (loss) on interest rate hedges	(151)			(151)
Distributions	(6,119)	(334)	(5,785)
Ending Balance at Jun. 30, 2023	288,809	$ (4,103)	$ 307,199	(14,287)
Ending Balance, Unit at Jun. 30, 2023		326	35,603
Beginning Balance at Sep. 30, 2023	263,724	$ (4,615)	$ 281,862	(13,523)
Beginning Balance, unit at Sep. 30, 2023		326	35,603
Net income (loss)	70,309	$ 637	$ 69,672
Unrealized gain on pension plan obligation	955			955
Tax effect of unrealized gain on pension plan obligation	(240)			(240)
Unrealized gain (loss) on captive insurance collateral	1,596			1,596
Tax effect of unrealized gain (loss) on captive insurance collateral	(336)			(336)
Unrealized gain (loss) on interest rate hedges	(1,007)			(1,007)
Tax effect of unrealized gain (loss) on interest rate hedges	270			270
Distributions	(18,689)	(1,041)	(17,648)
Retirement of units	(9,029)		$ (9,029)
Retirement of units, shares			(829)
Ending Balance at Jun. 30, 2024	307,553	$ (5,019)	$ 324,857	(12,285)
Ending Balance, Unit at Jun. 30, 2024		326	34,774
Beginning Balance at Mar. 31, 2024	331,135	$ (4,544)	$ 348,382	(12,703)
Beginning Balance, unit at Mar. 31, 2024		326	35,372
Net income (loss)	(11,044)	$ (101)	$ (10,943)
Unrealized gain on pension plan obligation	317			317
Tax effect of unrealized gain on pension plan obligation	(80)			(80)
Unrealized gain (loss) on captive insurance collateral	401			401
Tax effect of unrealized gain (loss) on captive insurance collateral	(84)			(84)
Unrealized gain (loss) on interest rate hedges	(186)			(186)
Tax effect of unrealized gain (loss) on interest rate hedges	50			50
Distributions	(6,455)	(374)	(6,081)
Retirement of units	(6,501)		$ (6,501)
Retirement of units, shares			(598)
Ending Balance at Jun. 30, 2024	$ 307,553	$ (5,019)	$ 324,857	$ (12,285)
Ending Balance, Unit at Jun. 30, 2024		326	34,774