Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2015
Selected Quarterly Financial Data [Line Items]
Sales	$ 181,584		$ 225,801		$ 532,052		$ 384,118		$ 162,064		$ 218,194		$ 462,025		$ 319,055		$ 1,323,555		$ 1,161,338		$ 1,674,291
Gross profit for product, installation and service	42,467		63,309		184,685		118,038		41,799		61,354		183,303		106,041		408,499		392,497
Operating income (loss)	(27,126)		(19,811)		69,032		33,237		(29,606)		(2,955)		96,319		23,646		55,332		87,404		93,613
Income (loss) before income taxes	(29,092)		(21,766)		66,996		31,138		(31,923)		(4,993)		94,113		21,475		47,276		78,672		70,391
Net income (loss)	(17,747)		(13,332)		39,704		18,275		(19,095)		(3,238)		55,209		12,058		26,900		44,934		37,556
Limited Partner interest in net income (loss)	$ (17,644)		$ (13,253)		$ 39,471		$ 18,170		$ (18,985)		$ (3,219)		$ 54,896		$ 11,990		$ 26,744		$ 44,682		$ 37,344
Net income (loss) per Limited Partner unit:
Basic and diluted	$ (0.32)	[1]	$ (0.24)	[1]	$ 0.59	[1]	$ 0.28	[1]	$ (0.34)	[1]	$ (0.06)	[1]	$ 0.79	[1]	$ 0.19	[1]	$ 0.46	[1],[2]	$ 0.70	[1],[2]	$ 0.59	[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 17 - Earnings Per Limited Partner Units.