Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Sep. 30, 2025		Jun. 30, 2025		Mar. 31, 2025		Dec. 31, 2024		Sep. 30, 2024		Jun. 30, 2024		Mar. 31, 2024		Dec. 31, 2023		Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2023
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 247,692		$ 305,618		$ 743,045		$ 488,063		$ 240,331		$ 331,640		$ 666,032		$ 528,096		$ 1,784,418		$ 1,766,099		$ 1,952,862
Gross profit for product, installations and services	59,425		85,857		259,885		157,699		57,880		88,247		206,046		149,651		562,866		501,824
Operating income (loss)	(40,943)		(19,177)		125,372		49,219		(48,559)		(12,291)		100,331		21,621		114,471		61,102		62,545
Income (loss) before income taxes	(40,594)		(23,090)		120,678		45,908		(50,642)		(15,201)		96,244		18,153		102,902		48,554		45,929
Net income (loss)	(28,671)		(16,629)		85,911		32,884		(35,086)		(11,044)		68,374		12,979		73,495		35,223		31,945
Limited Partner interest in net income (loss)	$ (28,396)		$ (16,472)		$ 85,109		$ 32,577		$ (34,760)		$ (10,943)		$ 67,754		$ 12,861		$ 72,818		$ 34,912		$ 31,657
Net income (loss) per Limited Partner unit:
Basic and diluted income per Limited Partner Unit:	$ (0.84)	[1]	$ (0.48)	[1]	$ 2.01	[1]	$ 0.79	[1]	$ (1.00)	[1]	$ (0.31)	[1]	$ 1.56	[1]	$ 0.32	[1]	$ 1.82	[1],[2]	$ 0.90	[1],[2]	$ 0.81	[2]

[1] The sum of the quarters do not add-up to the total due to the weighting of Limited Partner Units outstanding, rounding or the theoretical effects of FASB ASC 260-10-45-60 to Master Limited Partners earnings per unit.

[2] See Note 19 - Earnings Per Limited Partner Units.