Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended															12 Months Ended
	Sep. 30, 2021		Jun. 30, 2021		Mar. 31, 2021		Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020	Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2021		Sep. 30, 2020		Sep. 30, 2019
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 236,551		$ 283,100		$ 604,115		$ 373,320		$ 183,295		$ 232,155	$ 543,063		$ 508,945		$ 1,497,086		$ 1,467,458		$ 1,753,872
Gross profit for product, installation and service	49,491		70,091		226,202		131,870		46,818		84,159	196,440		147,603		477,654		475,020
Operating income (loss)	(30,517)		(13,764)		119,695		54,786		(36,098)		498	86,117		42,451		130,200		92,968		37,350
Income (loss) before income taxes	(32,629)		(15,963)		117,316		52,688		(44,051)		(2,051)	83,108		39,537		121,412		76,543		25,154
Net income (loss)	(23,233)		(12,054)		85,164		37,860		(30,199)		(46)	58,408		27,755		87,737		55,918		17,637
Limited Partners’ interest in net income	$ (23,043)		$ (11,956)		$ 84,483		$ 37,564		$ (29,976)		$ (45)	$ 57,999		$ 27,563		$ 87,048		$ 55,541		$ 17,542
Net income (loss) per Limited Partner unit:
Basic and diluted income per Limited Partner Unit:	$ (0.58)	[1]	$ (0.30)	[1]	$ 1.71	[1]	$ 0.74	[1]	$ (0.68)	[1]		$ 1.03	[1]	$ 0.49	[1]	$ 1.82	[1],[2]	$ 1.07	[1],[2]	$ 0.35	[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.