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, 2020	$ 255,820	$ (2,506)	$ 273,283	$ (14,957)
Beginning Balance, unit at Sep. 30, 2020		326	43,328
Net income (loss)	110,970	$ 879	$ 110,091
Unrealized gain on pension plan obligation	704			704
Tax effect of unrealized gain on pension plan obligation	(193)			(193)
Unrealized loss on captive insurance collateral	(913)			(913)
Tax effect of unrealized loss on captive insurance collateral	193			193
Unrealized gain on interest rate hedges	1,303			1,303
Tax effect of unrealized gain on interest rate hedges	(344)			(344)
Distributions	(17,535)	(735)	(16,800)
Retirement of units	(36,682)		$ (36,682)
Retirement of units, shares			(3,697)
Ending Balance at Jun. 30, 2021	313,323	$ (2,362)	$ 329,892	(14,207)
Ending Balance, Unit at Jun. 30, 2021		326	39,631
Beginning Balance at Mar. 31, 2021	337,276	$ (1,991)	$ 353,793	(14,526)
Beginning Balance, unit at Mar. 31, 2021		326	40,199
Net income (loss)	(12,054)	$ (98)	$ (11,956)
Unrealized gain on pension plan obligation	234			234
Tax effect of unrealized gain on pension plan obligation	(65)			(65)
Unrealized loss on captive insurance collateral	(47)			(47)
Tax effect of unrealized loss on captive insurance collateral	11			11
Unrealized gain on interest rate hedges	252			252
Tax effect of unrealized gain on interest rate hedges	(66)			(66)
Distributions	(6,002)	(273)	(5,729)
Retirement of units	(6,216)		$ (6,216)
Retirement of units, shares			(568)
Ending Balance at Jun. 30, 2021	313,323	$ (2,362)	$ 329,892	(14,207)
Ending Balance, Unit at Jun. 30, 2021		326	39,631
Beginning Balance at Sep. 30, 2021	278,204	$ (2,821)	$ 295,063	(14,038)
Beginning Balance, unit at Sep. 30, 2021		326	39,046
Net income (loss)	85,281	$ 726	$ 84,555
Unrealized gain on pension plan obligation	672			672
Tax effect of unrealized gain on pension plan obligation	(167)			(167)
Unrealized loss on captive insurance collateral	(3,486)			(3,486)
Tax effect of unrealized loss on captive insurance collateral	735			735
Unrealized gain on interest rate hedges	2,890			2,890
Tax effect of unrealized gain on interest rate hedges	(768)			(768)
Distributions	(17,350)	(821)	(16,529)
Retirement of units	(27,309)		$ (27,309)
Retirement of units, shares			(2,583)
Ending Balance at Jun. 30, 2022	318,702	$ (2,916)	$ 335,780	(14,162)
Ending Balance, Unit at Jun. 30, 2022		326	36,463
Beginning Balance at Mar. 31, 2022	340,354	$ (2,524)	$ 357,020	(14,142)
Beginning Balance, unit at Mar. 31, 2022		326	36,950
Net income (loss)	(10,587)	$ (93)	$ (10,494)
Unrealized gain on pension plan obligation	224			224
Tax effect of unrealized gain on pension plan obligation	(61)			(61)
Unrealized loss on captive insurance collateral	(812)			(812)
Tax effect of unrealized loss on captive insurance collateral	171			171
Unrealized gain on interest rate hedges	623			623
Tax effect of unrealized gain on interest rate hedges	(165)			(165)
Distributions	(5,918)	(299)	(5,619)
Retirement of units	(5,127)		$ (5,127)
Retirement of units, shares			(487)
Ending Balance at Jun. 30, 2022	$ 318,702	$ (2,916)	$ 335,780	$ (14,162)
Ending Balance, Unit at Jun. 30, 2022		326	36,463